Perspective Special Focus Issue: Clinical Chemistry

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Dried blood spot analysis to assess medication adherence and to inform personalization of treatment

Little research using dried blood spot samples to assess adherence to medication has been reported. The World Health Organisation estimates that only half of the patients in the developed world take their medication as prescribed. Additional costs to the healthcare provider include wasted medicines, avoidable additional hospital visits and non-optimum patient care. There is little evidence of information concerning medication adherence being made available to inform clinical decision making. In this article we explore the potential of the dried blood spot sample collection methodology as a means of identifying medication adherence to facilitate medicines optimization for a range of disparate diseases. Furthermore, the opportunity to personalize healthcare for different patients by assessing the clinically necessary therapeutic level of the relevant drugs is highlighted.

Background This article communicates the authors’ perspective on the use of dried blood spot (DBS) technology for assessing patient adherence to medications, which is a major problem worldwide. We are aware that the majority of readers of this journal are familiar with the use of DBS in drug discovery and development. In this paper we ask if the ‘simplicity’ of the DBS sampling technique can be used to ensure more patients worldwide demonstrate good adherence, i.e. use medicines as prescribed. This will avoid waste of the pharmaceutical industries’ efforts, the health service provider’s resources and more importantly will improve overall patient well being. At a point when care is ever more dependent on medication therapy for treating an ever growing number of patients improving medication adherence is possibly the major challenge for healthcare systems. This article looks at various clinical conditions in which DBS technology has been investigated to assess medication adherence and offers our thoughts in the area for the future.

10.4155/BIO.14.189 © 2014 Future Science Ltd

Sangeeta Tanna*,1 & Graham Lawson1 1 Leicester School of Pharmacy, Faculty of Health & Life Sciences, De Montfort University, The Gateway, Leicester, LE1 9BH, UK *Author for correspondence: [email protected]

What is medication adherence & the consequences of non-adherence? Patient non-adherence with prescription regimens is one of the most understated problems in healthcare systems worldwide. For example, only approximately 20% of some oral cancer therapy patients and 40% of cardiovascular therapy patients take their medicines as prescribed. Medication adherence usually refers to whether patients take their medications exactly to doctor’s recommendations (e.g., twice daily) as well as whether they continue to take a prescribed medication [1] . Proper adherence to a medication involves six key factors [2] : • The right drug; • At the right dose; • At the right time; • On the right schedule; • Under the right conditions; part of

• With the right precautions.

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 Tanna & Lawson

Key terms Dried blood spot: Drop of blood from a finger or heel prick, typically between 20 and 40 μl collected on filter paper and allowed to dry under ambient conditions to give a spot between 0.5 and 1.0cm in diameter. This is subsequently solvent extracted for analysis. Adherence: Sometimes referred to as compliance, presumes an agreement between prescriber and patient about the prescriber’s recommendations. Adherence to medicines is defined as the extent to which the patient’s actions matches the agreed recommendations.

Medication non-adherence is a growing concern to clinicians, healthcare systems, and other stakeholders (e.g., payers). because of mounting evidence that it is prevalent [3] . The World Health Organisation (WHO) reports that as high as 50% of the general population in developed countries are non-adherent to long-term therapies [4] . Non-adherence can be unintentional, for example, forgetting to take a dose. It can sometimes be intentional, for example. deliberately skipping a dose to try to avoid side effects or because of concerns about the expense of the drug. It can be defined by several behavioural patterns, including failure to collect prescriptions, failure to follow day-to-day instructions (e.g., taking too few or too many doses, or taking medication with inappropriate food) and failure to collect subsequent prescriptions as directed. Either way, the outcomes for the patient can be risky [1,2] . There are several explanations [1,5–7] for non-adherence including: • Medication factors such as regimen complexity and concern over side effects; • Patient factors such as denial of illness, cost of medication, physical problems, mental health, the assumption that medication can be discontinued if one feels better, and forgetfulness; • Polypharmacy situations, for instance with the elderly, patients may have up to ten medicines per prescription and complying with medication instructions can be particularly daunting and so all pills are taken at the same time; • Prescriber and pharmacy factors including poor patient communication, lack of information for the patient and inadequate compliance counselling, often limited by time constraints. Non-adherence is not a trivial situation. Across Europe there is a regional variation between 20 and 60% of patients do not take their medication according to prescription whilst in the USA the figure is

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approximately 50% [8] . But average figures do not give a real feel for the wide variations that occur. For oncology, published results show adherence rates which differ widely depending on the illness: 17–27% for hematological malignancies, 53–98% for breast cancer and 97% for ovarian cancer [9] . Patients taking cardiovascular (CV). medication exhibit similar variations in adherence [10] . In the USA after hospitalization for acute myocardial infarction, less than 75% of patients collect their medication within 7 days of discharge. Furthermore 34% of patients stopped taking at least one medication and 12% stopped all medication within a month of being discharged from hospital. Consistent use of medication over a 6–12 month period was found to be low: 56% non-adherent for statins and 54% non-adherent for b-blockers [3,11] . Non-adherence can have a negative impact on the efficacy of treatments and patient’s well-being. For example 194,500 deaths annually in the EU result from mis-dose and non-adherence to prescribed medication [12] . The healthcare professional will have uncertain knowledge of the patient’s real response to the prescribed medication. Furthermore non-adherence results in additional use of scarce healthcare resources and is associated with higher costs of care resulting either from unused medication (approximately GB£100 million in the UK) or from additional but avoidable hospitalization. In the USA the overall extra hospitalization cost is estimated to be approximately US$200 billion, where improving medication adherence is one facet of the Medicare Hospital Re-admissions Reduction Program (HRRP), which provides financial incentives to hospitals to lower re-admission rates [13] . Established as part of the US Affordable Care Act of 2010 the HRRP aims to reduce the number of patients being re-hospitalized within 30 days of an initial hospital stay as it is estimated that 75% of these were preventable with a potential cost saving of $12 billion [14] . Currently the financial incentives (penalties) may amount to a 2% reduction in the total patient charges paid to the hospital based on the re-admission of Medicare patients who originally went into hospital with one of three conditions: heart attack, heart failure or pneumonia. In the UK there is also concern over the 30-day re-admission rates and a similar use of financial incentives to improve the situation has been introduced [15] . In the UK the NHS has opted to specify which disease states will be excluded from this protocol and these include cancer care, all children under 17, maternity, mental health, end of life care and definitive treatment adjustment. Given the serious consequences of non-adherence to medication it is not surprising that much effort has been

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Dried blood spot analysis to assess medication adherence & to inform personalization of treatment

expended to identify methods to increase adherence. Indeed the WHO has declared that more people worldwide would benefit from efforts to improve medication adherence rather than the development of new medical treatments [4] . Whilst ideas including increased involvement of community pharmacists, E-prescribing, greater patient involvement and more clinical staff training have all been aired [16] there is currently no formal legislation in this area. However, a range of Guidelines in the following categories have been prepared: • Patient centred: increased education and awareness of medication, develop aids to improve adherence, for example the NICE Guideline 76: Medicines Adherence [17] ; • Clinician centred: the toolkits for Australian health professionals are good examples in this area particularly for cardiovascular care [18] ; • Health system solutions: more patient friendly, prescription monitoring, pill counts, direct observations and electronic monitoring; • Disease-specific: the NIH provides guidelines for the adherence to antiretroviral therapy, for example [19] . To improve healthcare outcomes clinicians ideally need to know the level of adherence in order to pro-

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vide maximum benefit for the patient. Many methods have been used to measure adherence, each of which has its limitations as summarized in Table 1 [1,20–21] . Adherence to medication can be measured by indirect assessment methods which include pill counts, patient questionnaires, electronic monitors, patient diaries. Whilst these assessments are relatively easy to carry out they do not always provide the required information. For instance pill counts do not provide information of other aspects of taking medications, such as dose timing which may be important in determining clinical outcomes. Direct assessment, for example, observation of the therapy or the determination of the change is a physical attribute e.g. blood pressure for a hypertensive patient is more costly in terms of both patient and clinician time. The costs associated with direct assessment can be reduced without detriment to the information produced, for example, the self measurement of the glucose level in a finger prick blood sample for the control of diabetes or the level of the prescribed drug in a similar blood sample self collected as a DBS. The value of the DBS sampling platform

This sampling technique has many readily recognized advantages but for several applications there remain difficulties to be overcome. The advantages include:

Table 1. Current methods used to assess adherence. Method

Comments

Outcomes

Patient interview

Non-invasive/easy/inexpensive/ global

Optimistic/interviewer dependent/too subjective

Patient diary

Non-invasive/self-report/ inexpensive/global

Optimistic/no confirmation of use/ diary must be returned

Pill count

Non-invasive/easy/inexpensive/ global

No confirmation of use or adherence/ pills may be lost or sold

Questionnaire

Non-invasive/must collect data/ global

No confirmation of use/no continuous data

Electronic monitoring

Non-invasive/expensive/globally difficult 

May be manipulated

Pharmacy records

Non-invasive/long-term records/ globally difficult

Drug regimen confirmed/no confirmation of adherence

Patient observation

Non-invasive/time consuming/ global

Confirmation only during clinics

Drug bio-marker

Invasive/expensive equipment/ globally difficult

Confirms recent use/patient PK data/ derived blood drug levels

Plasma drug levels/objective

Invasive/costly transport and technique/globally difficult

Confirms recent use/patient PK data/ measured blood drug levels

Urine drug levels

Non-invasive/costly transport and analysis / globally difficult

Confirms recent use/patient PK data/ objective

Data taken from [1,20,21].

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 Tanna & Lawson • Small volume blood sample; • Minimally invasive sample collection ideal for neonates, children and the elderly; • Ease of sample collection – easy access to cheap multiple samples to aid adherence checks; • May be used for patient self-sample collection in the home; • Ease of sample handling – transport constitutes a major saving versus liquid blood; • Potential for therapeutic drug monitoring. The problems associated with this approach include: • The potential value of the DBS samples depends on where you are in the world; • There is no low cost equipment available to analyse a DBS sample especially for point of care applications in low resource countries [22] ; • Apparent lack of communication between different users in disparate health applications; • Some concerns over quantification with respect to haematocrit; • Despite the development of several portable instruments to assess HIV at the point of care DBS samples will still be required for PCR analysis for validation tests. Once collected the DBS sample could be mailed to a laboratory for the subsequent analysis but this would involve delays during which time the impetus to maintain adherence to treatment could be lost. The use of DBS samples to improve patient outcomes Optimal patient outcomes require adherence, education, communication, on-going monitoring and follow-up [23] . To date measurement of patient mediKey terms Pharmacokinetics (PK): Provides a mathematical basis to assess the time course of drugs in the body. It enables the following processes to be quantified: Absorption, Distribution, Metabolism and Excretion. These processes referred to as ADME determine the drug concentrations in the body when medicines are prescribed. PCR: A biochemical technology used to amplify copies of a piece of DNA across several orders of magnitude. This technique is used in the diagnosis of hereditary diseases and the detection and identification of infectious diseases using genetic fingerprints.

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cation adherence and use of interventions to improve adherence is rare in routine clinical practice. Indeed in the UK the National Institute for Health and Clinical Excellence (NICE) [17] states that: ‘assessing adherence is not about assessing patients’. Bearing this in mind the required assessment may be restated as: ‘has the prescribed drug regimen produced the necessary therapeutic levels to benefit the patient?’ In principal therefore any of the published methods for determining therapeutic drug levels in DBS samples should be amenable to this task [24] . The DBS approach provides the healthcare professionals with the opportunity to provide more individualised patient care since the effects of different pharmacokinetic (PK) [25] and pharmacogenetic [26] parameters, on the target drug levels, will be detected. As a note of caution several different modes of detection [27] are used with the DBS platform, even for the same disease state and care must be taken to ensure that the results are directly comparable from each system. DBS-based examples of medication adherence & medication assessment in different diseases HIV-AIDS

The analysis of DBS continues to be used to monitor HIV infection/re-infection using PCR techniques [28] and adherence to anti-retroviral therapies (ART) using either HPLC or LC–MS/MS systems [29] . Sample integrity can be maintained when ‘cold chain’ transport is unavailable and PCR analysis of DBS samples is the most effective technology for the diagnosis of HIV infections in children. However, in Zambia, which has one of the world’s highest HIV rates, in 2012 there were only three PCR instruments dedicated to this work [30] . Where facilities are available the DBS sampling platform can also be used to identify prior exposure to, or adherence with, appropriate drug therapies [31,32] . In 2014 approximately 35 million people were living with HIV disease [33] . A significant proportion of these live in low- and middle-income countries where access to treatment rose from 5% to 50% between 2002 and 2008. The combination of available generic low cost antiretroviral drugs and DBS monitoring of both the viral load and the ART has made this widespread treatment campaign viable. Early reports have shown that identification of the disease and assessment of the levels of adherence to therapy are similar to those observed in industrialised countries [32–34] . Conventional assessment of HIV patients is based on a measure of the number of HIV-RNA units/ml of plasma (viral load) and replacing the liquid with a DBS offers many potential cost and efficiency savings. The principal areas of concern were the detection capabili-

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Dried blood spot analysis to assess medication adherence & to inform personalization of treatment

ties of the absolute viral load, which depended on the amplification factor of the system used and the initial quantification of the blood sample collected. Studies in well-equipped laboratories under standard conditions showed that viral load measurements of HIV-RNA could be replicated between plasma and DBS samples [35–37] . In order to improve detection limits for the DBS samples the entire spot was punched out and two spots were combined in the extraction process. The correlation between the two sampling techniques decreased below 5000 units/ml depending on the assay used. To determine if similar results could be obtained in a more resource limited setting in rural Tanzania, Johanessen et al. [38] compared 98 Plasma-DBS pairs in which the viral load ranged from 97% adherence from the carers of a selected group from the 606, the treatment failure rates indicated by the PCR analyses of the DBS samples were higher than expected from treatment efficacy studies [62] . Taneja et al. have reviewed the use of DBS in the bioanalysis of antimalarials and whilst they acknowledge the value of the reduction in sample volume they cite problems with the quantification of artemisinin derivatives [63] . These compounds decompose in the presence of iron (II) and are therefore long term unstable in a blood spot. This correlates with the observations of Blessborn et al. who cited the necessity of using only short storage times [59] . Counterfeit or substandard antimalarial medicines are widespread in Africa and Asia [55,63] and yet no account has been cited for the contribution of these materials to the levels of non-adherence. An identified absence or low level of the target therapeutic drug in the DBS extract could play an important part in assessing the exposure to counterfeit medicines.

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Dried blood spot analysis to assess medication adherence & to inform personalization of treatment

Epilepsy

• Patient 1:

Antiepileptic drugs (AED) are the mainstay for the control of seizures in the management of epilepsy [64] . Measuring AEDs in serum or plasma as an aid to personalising drug therapy is now a well established practice in the treatment of epilepsy [65] . Regular monitoring of AED serum concentrations is especially important to: • Assess the ‘individual therapeutic range’ especially for children; • Determine the resultant level from any dose change especially for those AEDs that have dose-dependent PK; • Investigate a possible fast metaboliser non-compliance with medication;

or

• Investigate possible PK variations particularly for children, in pregnancy and for the elderly. Modi et al. [66] reported that because their medication adherence was not rigorously assessed 28 children from a cohort of 112 received uninformed medication changes for continued seizures. Patsalos and Berry [64] have reviewed the use of different biological matrices including blood, DBS, tears, sweat, cerebrospinal fluid, hair and saliva to monitor the AED levels. They concluded that patients preferred saliva samples over blood sampling but saliva samples may be more readily contaminated. The simple sample collection capability of DBS was used to focus on individual patient experiences as a function of the prescribed medication. Self-collection of DBS samples by a patient every two weeks during pregnancy was used by de Haan et al. [67] to monitor the levels of the antiepileptic drug lamotrigine (LTG) for comparison with conventional determinations of the levels in 11 other patients. The observed increase in seizures in nine out of 12 pregnancies was thought to be related to the measured decrease in the LTG level per unit dose with respect to the baseline by up to 40%. The LTG levels returned to baseline after delivery with some evidence of toxic effects for some patients. These variations were replicated in the DBS sample data where the patient declined any changes in the prescribed dose. This study protocol was modified by Wegner et al. [68] to use the serum concentration levels from DBS samples to inform the doses prescribed for two patients taking a combination of LTG and oxcarbazepine (OXC) during pregnancy. Baseline levels for both drugs were determined from DBS samples to give the serum reference ranges prior to pregnancy. The dose levels for the individual patients were adjusted to maintain the serum levels within the reference range as the pregnancies progressed:

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–– LTG initial 245 mg;max 675 mg;final 575 mg (patient choice). –– OXC initial 1800 mg;max 2400 mg; final 1800 mg. • Patient 2: –– LTG initial 300 mg;max 1000 mg;uncertain reduction by patient. –– OXC initial 600 mg; max 2100 mg; uncertain reduction by patient. A multiple-methods assessment of child adherence to AED medication reported by Shah et al. [69,70] included AED concentrations measured by DBS samples in combination with parent and child self-reporting and prescription refill data. The DBS samples were produced either by self-collection at home or during visits to the clinic. Anticipated drug levels in blood for levetiracetan (LVT), (LTG), Phenobarbital (PHB), carbamazepine (CBZ) and its metabolite carbamazepine(10,11)epoxide were micrograms per ml level and conventional HPLC analysis was appropriate. As part of this study the effects of different haematocrit levels over the range 30 - 55% were investigated and found to produce only a 5% variation around the median figure for this range for all the target analytes. The key findings were that 33 of the 100 children studied were non-adherent to their medication and that the DBS modes of sample collection could usefully be used in adherence assessment. In epilepsy the efficacy of the prescription regimen can be assessed from the frequency of seizures experienced by the patients and the DBS results demonstrate the different levels of medication needed for individual patients. Careful adherence to these drug regimens is required to maximise patient benefit. Asthma

In a very forward looking investigation in 1988 Rattenbury and Tsanakas [71] used the DBS sampling platform to assess levels of Theophylline in the blood of 100 children receiving treatment for asthma. One of the purposes of the work was to assess the willingness of patients from 14 months to 15 years old to provide DBS samples collected at home. Of the 62 samples returned 37 showed less than the therapeutic concentration of Theophylline, three that were at potentially toxic levels and six children had levels less than 0.1 mg/l suggesting they were non-adherent to the medication prescription. In a parallel indepen-

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 Tanna & Lawson dent study 43 blood samples were analysed from 38 of the same children and overall very similar results were obtained. The study confirmed the willingness of paediatric patients and their guardians to provide the samples and suggested that supervision of the sampling arrangements from outpatients clinics might improve adherence. Cardiovascular diseases

Cardiovascular diseases (CVD) are one of the biggest killers worldwide and in the UK accounted for one in three deaths in 2009 [72] . There is evidence to suggest that as many as 50–60% of patients prescribed cardiovascular medication do not adhere to their prescription regimen [73,74] . This non-adherence to cardiovascular medication is a growing concern to all healthcare providers because of its prevalence and its associated morbidity, mortality, medicines wastage and higher costs of care [3,75–77] . In the UK and USA the non-adherence to CVD drugs has led to major concerns over the high number of patients re-admitted to hospital within 30 days of discharge. In attempts to reduce this number funding is withdrawn from relevant hospitals in the UK whereas in the US Medicare imposes a ‘fine’ on the hospitals. In both countries the implied message is the same ‘you must provide better care for your discharged patients including improved adherence’. It is evident from the concerns cited above that nonadherence to CVD drugs produces major healthcare and financial problems. In order to address this problem Lawson and Tanna investigated the use of self-collected DBS samples to assess adherence to CVD drugs commonly prescribed in the UK [25,78–80] . Possible detection problems relating to the pharmacokinetic properties of the selected CVD drugs were investigated by using a group of carefully monitored volunteers. Within this group there were volunteers taking none or one or two of the selected drugs. The drugs chosen for this study were bisoprolol, ramipril and simvastatin. DBS samples, self-collected by the volunteers at different points during the prescription time cycle, were analysed by LC–HRMS in order to confirm the detection of the drugs known to be taken by each volunteer. This approach has several advantages: • Volunteers are in steady state medication; • Polypharmacy is often the case in CVD care and false positives may be identified if a particular target drug is known to be absent from the individual prescription; • False negatives resulting from interactions may be identified;

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drug-drug

• Metabolic/PK variations may be observed; • Trial of the DBS sample self-collection protocol. This approach confirmed the ability of the system to correctly identify the presence/absence of a target drug at any point in the prescription cycle [25,80] . Despite the use of a carefully monitored volunteer group one example of non-adherence was identified from the data recorded. An unexpectedly high level of Simvastatin in a DBS sample resulted from one volunteer who admitted taking all the pills together at the same time, rather than as prescribed, to ensure none were missed. The statin was prescribed to be taken at least 12 h after the CVD drugs. This does however demonstrate the potential of the approach to assess the adherence to the prescription regimen. Diabetes

Monitoring adherence is important to improve the metformin control of diabetes in order to prevent unneeded dose adjustment or adding more medication for those who simply have poor adherence [81] . In this targeted study to prevent toxic levels and to assess adherence 84 patients provided DBS samples during routine clinical visits. Analysis of DBS extracts using HPLC/UV produced a linear calibration range of 150–4000 ng/ml. The measured plasma metformin levels for these 84 patients ranged from 198–7479 ng/ml. These results led to the methodology being used to assess the relationship between the metformin level and the metabolic control of diabetes and also to monitor adherence [81] . DBS-based examples of assessment of lifestyle adherence in different diseases There are several disease states where the lifestyle is the dominant factor affecting the state of well being and medication is used to compensate for a lapse in the prescribed behaviour. Diabetes is a well understood example of this situation and the monitoring of blood sugar levels is a common way of assessing the state of a person’s compliance with requirements and as a possible precursor to additional medication. DBS sampling is not as convenient as other methodologies for the diabetes patient but it is used to investigate levels of medication in occurrences of Hepatitis C among ‘needle users’ and to assess dietary conditions for phenylketonuria (PKU) sufferers. Dietary adherence Phenylketonuria

Phenylketonuria (PKU) is an inborn error of metabolism that prevents the hydroxylation of phenylalanine (Phe) to tyrosine (Tyr) with a consequential decrease in

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Dried blood spot analysis to assess medication adherence & to inform personalization of treatment

the number of neurotransmitters leading to retardation and seizures [82] . Monitoring of the Phe levels is important to ensure that the amino acid levels are sufficient for the body’s requirements and also low enough to avoid damaging the central nervous system [83] . The generally accepted approach to the management of PKU is a strict diet where the amount of free protein is restricted to maintain the Phe level within the treatment range and to use Phe-free metabolic support (medical food). The aim is to maintain the Phe level below 6 mg/dl at least until age 6 years. Lifelong dietary adherence is very individualised and will depend on the acceptance of ‘medical foods’ and the willingness to follow a prescribed diet. There is therefore a need for a rapid, simple and accurate method of monitoring blood samples. Back in 1996 Wendel and Langenbeck [84] suggested that the control of PKU by daily monitoring of blood samples in a manner similar to diabetes control was possible. The methodology they suggested was a finger prick sample to form a blood spot which was posted to a laboratory for analysis. They also advocated training programs for both the parents and patients about the disease and dietary adherence. Gregory et al. [82] assessed results from different analytical methods by comparing data from liquid blood samples via an amino acid analyser (AAA) with data from DBS samples analysed by MS/MS methods. Samples were obtained from 25 female PKU patients aged between 12 and 24 years. Over a 3-day trial period a full range of samples were obtained from 22 patients and to avoid added stress the DBS samples were produced from the venous blood sample. No dietary imposed variation in the Phe blood levels over the three days study was reported. The authors stressed that the data from the AAA was consistently 19% higher than from the MS/MS and in this situation such differences could have serious implications for treatment. Laufman et al. [85] faced with the situation of nonadherence to the DBS sampling regimen intended to measure compliance with the dietary criterion, for a group of 8 children, resorted to referring the situation to the child protective services (CPS). The individual situation for each patient, particularly the reduced DBS submission rates were discussed with CPS staff. In most cases referrals resulted in a temporary increase in DBS submission rates but these rapidly decreased again. Two children were taken into care and subsequently returned home and maintained good DBS submission rates and Phe levels. Of the four patients with the highest average levels (14.8 mg/dl), two showed minimal reduction to 13.6 mg/dl and two showed an average level of 8.8 mg/dl after a second referral. All of these levels were higher than the recommended maximum of 6.0 mg/dl. This investigation demonstrated that CPS

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intervention did not provide sustained improvement in adherence in most cases and the potential for improved medical care was lost. Needle users & adherence Hepatitis C

Chronic hepatitis C (HCV) infection affects more than 200 million people worldwide and is set to increase significantly over the next 20 years [86,87] . London, in the UK, has around 53,000 people estimated to have HCV, of which 7386 have been diagnosed but it is surprising that only 800 a year are being treated. If this situation continues where the untreated HCV can lead to cirrhosis, cancer, liver failure and transplant, the expected costs to the NHS will be of the order of £8 billion over the next 30 years [88] . In the UK the main source of HCV is injecting drug users but testing and diagnosing such a group with venepuncture methods is difficult [88] due to: • Chaotic lifestyle; • Limitations on the number of trained staff; • Fear of being judged; • Difficulties in coping with the care system and local authorities; • Non-stable situation in prisons. In October 2010 DBS testing for blood borne viruses was introduced in England, Scotland and Wales [89] as an alternative to venipuncture following the reports of Hickman et al. [90] and Craine et al. [91] on the positive value of DBS testing in prison environments. The costeffectiveness of introducing the DBS approach to reach more patients either in addiction services or in prisons was questioned by Martin et al. [92] . Their economic modelling report produced a positive outcome for both situations provided that treatment could be maintained especially in the prisons. The value of the DBS approach for diagnosis in prisons was confirmed by Dodd et al. and they also cited that transfers within prisons were an impediment to adherence with treatment [93] . Tait et al. [94] also confirmed effectiveness of the DBS approach in a paper published in 2013, based on results from a ‘reallife’ study between 2009 and 2011. They concluded that the DBS test was cost effective both in terms of the cost per diagnosis (£30 per positive test for DBS versus £106 conventional) and the cost per entry into treatment. In this investigation 1123 DBS tests were carried out to identify blood borne viruses and subsequently assess the adherence to follow-up medication. The proportion of positive test results was higher for the DBS samples (35.3% versus 27.5%) this was pos-

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 Tanna & Lawson sibly due to providing drug users with easier access to blood borne virus testing rather than opportunistic testing in a clinic or prison. This easy access to testing was matched by the roll-out of a community pharmacy based DBS scheme in which more than 70 pharmacies deliver tests for hepatitis B and C. This is proving to be a popular choice because of the easy access and the lack of questioning when seeking the test [89] . In two parallel adherence trials to follow-up medication, assessed using DBS samples, Tait et al. [94] reported 100% adherence when the DBS samples were collected at a needle exchange centre. The results from samples collected at a drug treatment centre showed 83.3% adherence for 23 volunteers. One of the conclusions from this study was that the DBS platform should become a vital tool in controlling the HCV epidemic. Adherence: what does the future hold? Non-adherence to medicines continues to be a problem worldwide. NICE in the UK state [17] ‘‘nonadherence is common and that most patients are non-adherent sometimes’’. D’Amato has summarized the limitations of the standard adherence assessment methods including the possibility of deliberate misinformation supplied by the patients and suggests multimodal approaches are required [95] . This is echoed by Horne [96] , at a meeting on the European Union response to medication non-adherence, who stated that there is ‘no one size fits all’ for non-adherence and that people are individuals and the solutions to the problems of medical non-adherence should be ‘individualized’. This was also recognized as a means

to improve adherence to cardiovascular therapy but the need for additional clinical staff to implement and manage the interventions would increase the costs of care. There are therefore several future possibilities: • Continued development of new areas of application. Literature information indicates that research in monitoring and adherence is being carried out in the following areas tuberculosis medication [97] , oral cancer therapy [98] , transplant anti-rejection drugs [99,100] , dietary concerns particularly with respect to folate status [101] and on a much wider front in the national social life, health and aging project [102] ; • Develop and provide adherence assessment services from specialist private or healthcare based laboratories in a manner analogous to those available for newborn screening in the USA. Indeed even in the UK a private self-funded assessment test is available for vitamin D levels based on a self-sampled DBS platform [103] ; • Develop a generally available overall approach for the DBS platform not simply as a monitor of adherence to prescription but as a means to optimise healthcare in terms of ensuring that the appropriate level of therapeutic medication is achieved in individual patients. This will only be achieved if the prescribing clinician is aware of all the patient circumstances (adherence, other medication and PK and PG data).

Executive summary What is medication adherence & the consequences of non-adherence? • Adherence refers to whether patients take their prescribed medication(s) exactly as recommended. • Non-adherence is a growing problem worldwide and results in suboptimal patient care and is a major source of the extra costs of healthcare provision

The value of the dried blood spot sampling platform • The ease of use and low cost of the dried blood spot (DBS) sampling technique makes it ideal for adherence assessment purposes especially in countries with limited resources. Whilst the sampling technique is low cost and robust there remains the need for sophisticated laboratory analytical equipment.

The use of dried blood spot (DBS) samples to improve patient outcomes • Data from the DBS demonstrates the level of adherence and indicates the effectiveness of the prescription to attain therapeutic levels of the drug in the patient.

DBS-based examples of medication adherence and medication assessment in different diseases • Trials of DBS approach have been successfully performed for targeted diseases. • The DBS approach has been used across a wide spread of diseases including HIV-AIDS, malaria, epilepsy, asthma, cardiovascular diseases and diabetes.

DBS-based examples of assessment of lifestyle adherence in different diseases • The DBS approach has also been used to assess adherence to lifestyle markers for various diseases: for example phenylketonuria and hepatitis C.

Adherence: what does the future hold? • DBS data can answer the question of adherence to medication which is an integral part of the determination of the optimum level of the appropriate drug/s for each individual patient.

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Dried blood spot analysis to assess medication adherence & to inform personalization of treatment

Future perspective DBS sampling provides the basis for newborn screening programs now common practice around the world. This established capability should be expanded to monitor drug levels in patients with critical illnesses in order to enable clinicians and pharmacists to optimize and individualize the healthcare offered to the patient. The question of adherence to medication is an integral part of the determination of the optimum level of the appropriate drug/s for a particular patient based on the DBS data. The patient can become involved in the healthcare process when the optimisation of the medication prescription based on DBS data is explained to them. The concept of a ‘personalized for you’

medication care scheme could become routine and lead to long term savings for the healthcare provider by improving patient outcomes, optimizing medicine usage and eliminating untimely re-admissions. Financial & competing interests disclosure The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties. No writing assistance was utilized in the production of this manuscript. 11

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Dried blood spot analysis to assess medication adherence & to inform personalization of treatment

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