Journal of Virological Methods 196 (2014) 15–17
Contents lists available at ScienceDirect
Journal of Virological Methods journal homepage: www.elsevier.com/locate/jviromet
Short communication
Comparison of automated chemiluminescence immunoassays with capture enzyme immunoassays for the detection of measles and mumps IgM antibodies in serum Becky Haywood ∗ , Mauli Patel, Samantha Hurday, Ruth Copping, Daniel Webster, Dianne Irish, Tanzina Haque Department of Virology, Royal Free London NHS Foundation Trust, London, UK
s u m m a r y Article history: Received 5 August 2013 Received in revised form 15 October 2013 Accepted 18 October 2013 Available online 30 October 2013 Keywords: Measles Mumps Immunoassay
Outbreaks of measles and mumps occur regularly in the UK. Rapid diagnosis of acute infection is important for both infection control and epidemiological purposes. The objective of this study was to compare the performance of an automated platform (DiaSorin Liaison® , Saluggia, Italy) with a manual capture enzyme immunoassay (EIA; Microimmune, Hounslow, UK) for the detection of measles and mumps IgM antibodies in serum from symptomatic individuals. Ninety sera tested previously for measles (n = 50) and mumps (n = 40) IgM using the manual EIA were tested retrospectively using the DiaSorin Liaison® and the results compared. Sensitivity, specificity, inter-assay variability and intra-assay variability of the Liaison® assays were calculated. Sensitivity and specificity of the Liaison® assay for measles IgM were 92% and 100% respectively, with inter-assay variation of 14.1% and intra-assay variation of 12.5%. The sensitivity and specificity of the mumps IgM Liaison® assay were 88% and 95% respectively, with an inter-assay and intra-assay variation of 13.9% and 5.3% respectively. Both the measles and mumps IgM Liaison® assays gave fewer equivocal results than the EIA. Neither Liaison® IgM assay showed any cross-reactivity with sera positive against other viruses, however the measles IgM EIA cross-reacted with parvovirus IgM. The automated Liaison® assays are more specific, cheaper and less labour-intensive compared to the manual EIA. The Liaison® assays benefit from reduced number of equivocal results compared to the EIA for both measles and mumps IgM. This allows clinical decisions to be made accurately and in a timely manner. © 2013 Elsevier B.V. All rights reserved.
Despite the availability of an effective and safe vaccine, outbreaks of measles (Vivancos et al., 2012) and mumps (Kay et al., 2011) continue to occur in the UK. According to recent data from Health Protection Agency (2013), only 89% of UK 5 year olds currently receive their second dose of measles, mumps and rubella (MMR) vaccine; this is much lower than the 95% coverage required to interrupt measles transmission (World Health Organisation, 2003). This report also highlights regional differences in MMR uptake within the UK, with England having poorer MMR vaccination rates (88.5%) than the devolved administrations (≥90%). Both measles and mumps are notifiable diseases in the UK (Department of Health, 2010). Measles is highly infectious and can pose a major infection control issue in community and hospital settings (Botelho-Nevers et al., 2012). Rapid diagnosis of acute measles
∗ Corresponding author. Present address: Virus Reference Department, Reference Microbiology Services, Public Health England, London NW9 5EQ, UK. E-mail address: [email protected] (B. Haywood). 0166-0934/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jviromet.2013.10.027
cases is important for epidemiology, case isolation and contact tracing. Once the immune status (presence or absence of IgG antibody) of any contacts is ascertained, prophylactic MMR vaccination can be administered if required. In addition, normal human immunoglobulin can be given to those in whom vaccination is contraindicated, such as pregnant women and immunocompromised individuals, who are at higher risk of developing measles-related complications such as pneumonitis, encephalitis, convulsions and death. Although in childhood mumps usually follows an uneventful course, neurological involvement occurs in around 50% of those infected, ranging from asymptomatic involvement to aseptic meningitis. Infections in the post-pubescent may lead to complications such as orchitis, oophoritis and pancreatitis (Galazka et al., 1999). Rare cases of encephalitis and hearing loss can also occur. The Liaison® measles IgM and mumps IgM are indirect chemiluminescence immunoassays for use on the DiaSorin Liaison® automated analyser. The analyser can perform in random access and batch testing modes, with each assay completed in around 1 h with minimum staff labour. The Microimmune capture
16
B. Haywood et al. / Journal of Virological Methods 196 (2014) 15–17
Table 1A Measles IgM: comparison between DiaSorin Liaison® and Manual EIA. Microimmune measles IgM
®
Liaison measles IgM
Positive Equivocal Negative
Total
Positive
Equivocal
Negative
Total
22 1 2
0 0 3
0 0 22
22 1 27
25
3
22
50
Table 1B Mumps IgM: comparison between DiaSorin Liaison® and manual EIA. Microimmune/reference lab mumps IgM
Liaison® mumps IgM Total
Positive Equivocal Negative
Positive
Equivocal
Negative
Total
7 1 1
0 0 9
1 0 21
8 1 31
9
9
22
40
enzyme immunoassays (EIA) for measles and mumps IgM require batch testing and take 2 h to complete, requiring approximately 35–45 min of staff hands-on time. The objective of this study was to compare the performance of the automated DiaSorin Liaison® platform with the manual Microimmune capture EIA (Microimmune Ltd., UK) for the detection of measles and mumps IgM in serum from symptomatic individuals. Ninety diagnostic sera previously tested for measles IgM (n = 50) and mumps IgM (n = 40) using the Microimmune EIA at the Royal Free Hospital between 2011 and 2012 were tested retrospectively using the Liaison® platform. All available EIA positive and equivocal specimens for each marker were tested by Liaison® . A selection of measles/mumps IgM EIA negative specimens were tested by Liaison® , including specimens positive for other viral markers to assess the impact of potential cross-reactivity. Inter-assay variability was calculated by running a specimen replicate 5 times on separate days, intra-assay variability was calculated by running a specimen replicate 5 times in one batch. All assays were performed and results interpreted according to the manufacturers’ instructions. The results of the measles IgM comparison are summarised in Table 1A. Twenty-two specimens were positive in both assays, with 22 negative in both. Three positive EIA specimens gave discrepant results by Liaison® : 1 equivocal and 2 negative. Three equivocal EIA specimens gave negative results by Liaison® . Specimens giving equivocal results in either assay were not included in calculations. The sensitivity and specificity of the Liaison® assay was 92% and 100% respectively. The Liaison® had a positive predictive value (PPV) of 100% and a negative predictive value (NPV) of 92%. Inter-assay variability was 14.1% and intraassay variability was 12.5%. The Cohen’s Kappa value was 0.96. The results of the mumps IgM comparison are summarised in Table 1B. Seven specimens were positive in both assays, with 21 negative in both. Two EIA positives gave discrepant results by Liaison® : 1 equivocal and one negative. Nine equivocal EIA specimens gave negative results when tested by Liaison® , and 1 EIA negative was reactive by Liaison® . Four specimens were sent for confirmatory testing to the Health Protection Agency reference laboratory – 2 EIA positive/Liaison® negative, one EIA positive/Liaison® equivocal, and one negative EIA/Liaison® positive. Numbers in Table 1B reflect the reference laboratory results in place of EIA results for those sent for confirmation. Specimens giving equivocal results in either assay were not included in calculations. The sensitivity and specificity of the
Liaison® mumps IgM assay was 88% and 95% respectively. The PPV was 88% and the NPV 95%. Inter-assay variability was 13.9%, intra-assay variability 5.3% and the Cohen’s Kappa value was 0.68. Three measles EIA positive specimens gave discrepant results by Liaison® : 2 negative and 1 equivocal. One was parvovirus IgM and DNA positive; the EIA result was reported to be a cross-reaction which the Liaison® assay correctly identified as negative. The second was from a patient who had contact with suspected measles 10 days prior, presenting with a sore throat, lymph node swelling and maculopapular rash. The date of onset of symptoms is unknown, and measles IgM may take up to 4 days post-rash to become detectable (Helfand et al., 1997). As the patient had contact with a known case it is likely that the sample was taken early in illness which may explain the negative IgM value, however this could not be confirmed as no follow-up specimens from this patient were received. The Liaison® equivocal was from a patient with hyper-IgM syndrome. All 3 measles EIA equivocal samples were negative by the Liaison® assay. Two were from the same patient taken 15 days apart with no increase in reactivity seen on either assay. This suggests that these equivocal results were due to false reactivity in the EIA. The third was from a patient with no clinical details indicating a rash, also suggesting a potential non-specific reaction. All 22 samples negative by the measles EIA were also negative with the Liaison® assay. Within this group were specimens known to be positive for mumps virus IgM, human immunodeficiency virus-1 (HIV-1) IgG, Epstein-Barr virus viral capsid antigen (EBV VCA) IgM, cytomegalovirus IgM, dengue virus IgM, rubella virus IgM, parvovirus IgM, hepatitis A virus IgG, hepatitis B surface antibody and hepatitis B core antibody. No cross-reaction with the Liaison® measles IgM kit was seen. The inter-assay coefficient of variation (CV) is acceptable at
Contents lists available at ScienceDirect
Journal of Virological Methods journal homepage: www.elsevier.com/locate/jviromet
Short communication
Comparison of automated chemiluminescence immunoassays with capture enzyme immunoassays for the detection of measles and mumps IgM antibodies in serum Becky Haywood ∗ , Mauli Patel, Samantha Hurday, Ruth Copping, Daniel Webster, Dianne Irish, Tanzina Haque Department of Virology, Royal Free London NHS Foundation Trust, London, UK
s u m m a r y Article history: Received 5 August 2013 Received in revised form 15 October 2013 Accepted 18 October 2013 Available online 30 October 2013 Keywords: Measles Mumps Immunoassay
Outbreaks of measles and mumps occur regularly in the UK. Rapid diagnosis of acute infection is important for both infection control and epidemiological purposes. The objective of this study was to compare the performance of an automated platform (DiaSorin Liaison® , Saluggia, Italy) with a manual capture enzyme immunoassay (EIA; Microimmune, Hounslow, UK) for the detection of measles and mumps IgM antibodies in serum from symptomatic individuals. Ninety sera tested previously for measles (n = 50) and mumps (n = 40) IgM using the manual EIA were tested retrospectively using the DiaSorin Liaison® and the results compared. Sensitivity, specificity, inter-assay variability and intra-assay variability of the Liaison® assays were calculated. Sensitivity and specificity of the Liaison® assay for measles IgM were 92% and 100% respectively, with inter-assay variation of 14.1% and intra-assay variation of 12.5%. The sensitivity and specificity of the mumps IgM Liaison® assay were 88% and 95% respectively, with an inter-assay and intra-assay variation of 13.9% and 5.3% respectively. Both the measles and mumps IgM Liaison® assays gave fewer equivocal results than the EIA. Neither Liaison® IgM assay showed any cross-reactivity with sera positive against other viruses, however the measles IgM EIA cross-reacted with parvovirus IgM. The automated Liaison® assays are more specific, cheaper and less labour-intensive compared to the manual EIA. The Liaison® assays benefit from reduced number of equivocal results compared to the EIA for both measles and mumps IgM. This allows clinical decisions to be made accurately and in a timely manner. © 2013 Elsevier B.V. All rights reserved.
Despite the availability of an effective and safe vaccine, outbreaks of measles (Vivancos et al., 2012) and mumps (Kay et al., 2011) continue to occur in the UK. According to recent data from Health Protection Agency (2013), only 89% of UK 5 year olds currently receive their second dose of measles, mumps and rubella (MMR) vaccine; this is much lower than the 95% coverage required to interrupt measles transmission (World Health Organisation, 2003). This report also highlights regional differences in MMR uptake within the UK, with England having poorer MMR vaccination rates (88.5%) than the devolved administrations (≥90%). Both measles and mumps are notifiable diseases in the UK (Department of Health, 2010). Measles is highly infectious and can pose a major infection control issue in community and hospital settings (Botelho-Nevers et al., 2012). Rapid diagnosis of acute measles
∗ Corresponding author. Present address: Virus Reference Department, Reference Microbiology Services, Public Health England, London NW9 5EQ, UK. E-mail address: [email protected] (B. Haywood). 0166-0934/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jviromet.2013.10.027
cases is important for epidemiology, case isolation and contact tracing. Once the immune status (presence or absence of IgG antibody) of any contacts is ascertained, prophylactic MMR vaccination can be administered if required. In addition, normal human immunoglobulin can be given to those in whom vaccination is contraindicated, such as pregnant women and immunocompromised individuals, who are at higher risk of developing measles-related complications such as pneumonitis, encephalitis, convulsions and death. Although in childhood mumps usually follows an uneventful course, neurological involvement occurs in around 50% of those infected, ranging from asymptomatic involvement to aseptic meningitis. Infections in the post-pubescent may lead to complications such as orchitis, oophoritis and pancreatitis (Galazka et al., 1999). Rare cases of encephalitis and hearing loss can also occur. The Liaison® measles IgM and mumps IgM are indirect chemiluminescence immunoassays for use on the DiaSorin Liaison® automated analyser. The analyser can perform in random access and batch testing modes, with each assay completed in around 1 h with minimum staff labour. The Microimmune capture
16
B. Haywood et al. / Journal of Virological Methods 196 (2014) 15–17
Table 1A Measles IgM: comparison between DiaSorin Liaison® and Manual EIA. Microimmune measles IgM
®
Liaison measles IgM
Positive Equivocal Negative
Total
Positive
Equivocal
Negative
Total
22 1 2
0 0 3
0 0 22
22 1 27
25
3
22
50
Table 1B Mumps IgM: comparison between DiaSorin Liaison® and manual EIA. Microimmune/reference lab mumps IgM
Liaison® mumps IgM Total
Positive Equivocal Negative
Positive
Equivocal
Negative
Total
7 1 1
0 0 9
1 0 21
8 1 31
9
9
22
40
enzyme immunoassays (EIA) for measles and mumps IgM require batch testing and take 2 h to complete, requiring approximately 35–45 min of staff hands-on time. The objective of this study was to compare the performance of the automated DiaSorin Liaison® platform with the manual Microimmune capture EIA (Microimmune Ltd., UK) for the detection of measles and mumps IgM in serum from symptomatic individuals. Ninety diagnostic sera previously tested for measles IgM (n = 50) and mumps IgM (n = 40) using the Microimmune EIA at the Royal Free Hospital between 2011 and 2012 were tested retrospectively using the Liaison® platform. All available EIA positive and equivocal specimens for each marker were tested by Liaison® . A selection of measles/mumps IgM EIA negative specimens were tested by Liaison® , including specimens positive for other viral markers to assess the impact of potential cross-reactivity. Inter-assay variability was calculated by running a specimen replicate 5 times on separate days, intra-assay variability was calculated by running a specimen replicate 5 times in one batch. All assays were performed and results interpreted according to the manufacturers’ instructions. The results of the measles IgM comparison are summarised in Table 1A. Twenty-two specimens were positive in both assays, with 22 negative in both. Three positive EIA specimens gave discrepant results by Liaison® : 1 equivocal and 2 negative. Three equivocal EIA specimens gave negative results by Liaison® . Specimens giving equivocal results in either assay were not included in calculations. The sensitivity and specificity of the Liaison® assay was 92% and 100% respectively. The Liaison® had a positive predictive value (PPV) of 100% and a negative predictive value (NPV) of 92%. Inter-assay variability was 14.1% and intraassay variability was 12.5%. The Cohen’s Kappa value was 0.96. The results of the mumps IgM comparison are summarised in Table 1B. Seven specimens were positive in both assays, with 21 negative in both. Two EIA positives gave discrepant results by Liaison® : 1 equivocal and one negative. Nine equivocal EIA specimens gave negative results when tested by Liaison® , and 1 EIA negative was reactive by Liaison® . Four specimens were sent for confirmatory testing to the Health Protection Agency reference laboratory – 2 EIA positive/Liaison® negative, one EIA positive/Liaison® equivocal, and one negative EIA/Liaison® positive. Numbers in Table 1B reflect the reference laboratory results in place of EIA results for those sent for confirmation. Specimens giving equivocal results in either assay were not included in calculations. The sensitivity and specificity of the
Liaison® mumps IgM assay was 88% and 95% respectively. The PPV was 88% and the NPV 95%. Inter-assay variability was 13.9%, intra-assay variability 5.3% and the Cohen’s Kappa value was 0.68. Three measles EIA positive specimens gave discrepant results by Liaison® : 2 negative and 1 equivocal. One was parvovirus IgM and DNA positive; the EIA result was reported to be a cross-reaction which the Liaison® assay correctly identified as negative. The second was from a patient who had contact with suspected measles 10 days prior, presenting with a sore throat, lymph node swelling and maculopapular rash. The date of onset of symptoms is unknown, and measles IgM may take up to 4 days post-rash to become detectable (Helfand et al., 1997). As the patient had contact with a known case it is likely that the sample was taken early in illness which may explain the negative IgM value, however this could not be confirmed as no follow-up specimens from this patient were received. The Liaison® equivocal was from a patient with hyper-IgM syndrome. All 3 measles EIA equivocal samples were negative by the Liaison® assay. Two were from the same patient taken 15 days apart with no increase in reactivity seen on either assay. This suggests that these equivocal results were due to false reactivity in the EIA. The third was from a patient with no clinical details indicating a rash, also suggesting a potential non-specific reaction. All 22 samples negative by the measles EIA were also negative with the Liaison® assay. Within this group were specimens known to be positive for mumps virus IgM, human immunodeficiency virus-1 (HIV-1) IgG, Epstein-Barr virus viral capsid antigen (EBV VCA) IgM, cytomegalovirus IgM, dengue virus IgM, rubella virus IgM, parvovirus IgM, hepatitis A virus IgG, hepatitis B surface antibody and hepatitis B core antibody. No cross-reaction with the Liaison® measles IgM kit was seen. The inter-assay coefficient of variation (CV) is acceptable at
