20 28 Bronshtein AM, Mironov SP, Silaev AV, Panteleeva EIA. Radionucleotide and sonographic diagnosis of lesions of the hepatobiliary system in opisthorchiasis. Med Parazitol (Mosk) 1989;5:13-17 [in Russian] 29 Chen MG, Mott KE. Progress in assessment of morbidity due to Fasciola hepatica infection: a review of recent literature. Trop Dis BullI99O;87:RI-R38 30 Rogan MT, Craig PS, Zeyhle E, Romig T, Lubano GM, Deshan L. Evaluation of a rapid dot-ELISA as a field test for the diagnosis of cystic hydatid disease. Trans R Soc Trop Hyg 1991;85(in press) 31 King DL. Ultrasonography of echinococcal cysts. J Clin Ultrasound 1973;1:64-7 32 Vicary FR, Cusick G, Shirley 1M, Blackwell RJ. Ultrasound and abdominal hydatid disease. Trans R Soc Trop Med Hyg 1977;71:29-31 33 Macpherson CNL, Romig T, ZeyhleE, Rees PH, Were lBO. Portable ultrasound scanner versus serology in screening for hydatid cysts in a nomadic population. Lancet 1987; 1:259-61 34 Craig PS, Zeyhle E, Romig T. Hydatid disease: research and control in Turkana, 11. The role of immunological techniques for the diagnosis of hydatid disease. Trans R Soc Trop Med Hyg 1986;80:183-92 35 Cossetto B, Gruenewald S, Antico V, Little lH. Albendazole treatment of recurrent hydatid disease: serial evaluation with ultrasound. Aust N Z J Surg 1989;59:933-6 36 Romig T, Zeyhle E, Macpherson CNL, Rees PH, Were lBO. Cyst growth and spontaneous cure in hydatid disease. Lancet 1986;ii:861 37 Macpherson CNL, Spoerry A, Zeyhle E, RomigT, Gorfe M. Pastoralists and hydatid disease: an ultrasound scanning prevalence survey in East Africa. Trans R Soc Trop Med Hyg 1989;84:243-7 38 Macpherson CNL, Wachira T, Zeyhle E, Romig T, Macpherson C. Hydatid disease - Research and control in Turkana, Kenya, IV. The control programme. Trans R Soc Trop Med Hyg 1986;80:196-200 39 Didier D, Weiler S, Rohmer P, et al. Hepatic alveolar echinococcosis: correlative US and CT study. Radiology 1985;154:179-86 40 Gottstein B, Tschudi K, Eckert r, Ammann R. Em2-ELISA for the follow-up of alveolar echinococcus after complete surgical resection of liver lesions. Trans R Soc Trop Med Hyg 1989;83:389-93 41 D'Alessandro A, Rausch RL, Cuello C, Aristizabal N. Echinococcus vogeli in man, with a review of polycystic hydatid disease in Colombia and neighbouring countries. Am J Trop Med Hyg 1979;28:303-17 42 Homeida MA, Mackenzie CD, Williams IF, Ghalib HW. The detection of onchocercal nodules by ultrasound technique. Trans R Soc Trop Med Hyg 1986;80:570-1 43 Poltera AA, Reyna 0, Zea Bores G, Nowellde Arevalo AM, Beltranena F. Detection of skin nodules in onchocerciasis by ultrasound scans. Lancet 1987;1:505 44 Leichsenring M, Troger r, Nelle M, Buttner DW, Darge K, Doehring-Schwerdtfeger E. Ultrasonographical investigations of onchocerciasis in Liberia. Am J Trop Med Hyg 1990;43:380-5 45 Poltera AA, Zea-Flores G, Guderian R, et al. Onchocercidal effects of amocarzine (CGP 6140) in Latin America. Lancet 1991;337:583-4

Tropical Doctor, January 1992

The provision of safe blood - policy issues in the prevention of human immunodeficiency virus transmission C J van Dam MD MSc'* L Fransen MD PhD'

D Sondag-Thull MD PhD 2

'AIDS Task Force, EEC, Brussels and "Service Transfusion Sanguine, Centre Hospitalier Universitaire de Liege TROPICAL DOCTOR,

1992, 22, 20-23

SUMMARY

The AIDS epidemic has focused attention on the constraints and deficiencies present in many blood transfusion services in the developing world. We discuss a variety of options for reducing transfusion-related HIV transmission, and suggest how new transfusion strategies may be implemented. We show that a transfusion service cannot rely solely on the screening of donor blood for anti-HIV antibodies and that a more comprehensive approach is needed. Important components of this approach include donor selection and improved clinical practice, in which blood and blood products are prescribed only when really necessary. INTRODUCTION

The blood borne character of AIDS was detected early in the epidemic, when AIDS in haemophiliacs and children was linked to transfusions of either blood components or bloodt-'. Efforts were made to ensure the safety of transfused blood, although no testing methods were then available. Focus was on the exclusion of donors with the then known high risk behaviours", Today a number of different interventions may contribute to the safety of a blood transfusion service and minimize the contribution of blood transfusion to the transmission of HIV. Options to reduce or prevent transmission of HIV through donor blood fall into four major categories. *Joined since submission the WHO STD Programme, Geneva

Tropical Doctor, January 1992

21

Table 1. Minimum estimates of the annual operating costs for a blood transfusion service, expressed per unit of collected blood US$/unit collected Essential supplies collection containers additional components test kits: HIV HBsAg Other serology reagents labels, cards, stationery Salaries 1 paid staff member for each 500 blood donations per annum; yearly salary cost is estimated at 5000 US$, or per donation Fixed costs, overheads fuel, telephone, utilities, legal requirements, building and equipment maintenance, depreciation and inflation; transport Total

2.00 1.50 1.50 1.50 1.00 1.00 1.00

lO.OO

20.00 40.00

(1) SELECTION OF DONORS AT REDUCED RISK OF INFECTION

Discarding blood, after having gone to the expense of collecting, storing and testing the blood, represents the loss of at least US$40 per unit discarded. Table I provides a breakdown of the minimum cost of a unit of tested blood in the developing world. (Note that the cost of ELISA screening represents only about 4010 of the total cost of providing one unit of tested blood for clinical use.) In Rwanda it has been possible, by selecting donors with low risk behaviour, to reduce the seroprevalence among donors by some 66%. A theoretical annual saving of US$16 000 has however largely been offset by the greatly increased cost of blood collection through mobile teams", Selection of donors brought the prevalence down from 25% to 5% in Uganda, with considerable savings and reduced false-positivity rates (Watson-Williams, personal communication). The situation is complicated by the fact that in many countries, for instance in West Africa and Latin America, no tradition of voluntary blood donation exists, and most donations are either of the replacement type or are bought from semi-professional donors. It has been shown that voluntary, non-remunerated donors are less likely to be infected with transfusion-transmissible diseases than either professional or replacement donors''-".

A shift toward voluntary donations will often require a strong condemnation or even prohibition by the Ministry of Health of paid donations. (2) SCREENING DONOR BLOOD FOR HIV ANTIBODIES

The latest generation screening tests for HIV -I, HIV-2, or combined HIV-112 tests are highly sensitive and specific in the detection of anti-HIV antibodies. There is still a risk however, that some seropositive blood will be recorded as seronegative'. This risk is related to the sensitivity of the test used, under field conditions, and to the prevalence of HIV infection in the donor population (the higher the seroprevalence, the greater the absolute number of false-negative results). A second shortcoming of serological testing is the well-known fact that antibodies are not present in the early phases of HIV infection. The present screening tests are all based on the detection of specific antibody; these tests will therefore not detect early infections. The seronegative incubation period is usually of the order of 6-8 weeks, but can occasionally be as long as 17 monthsv'". HIV antigen has been detected in patients with negative antibody tests!' and occasionally even patients with AIDS are negative for anti-HlV antibodiesl-, While this is of limited practical importance in a population with a low prevalence of HIV infection, it will lead to a considerable number of false-negative results in communities in which the seroprevalence rate is high. An analysis of the existing blood transfusion service (BTS) should precede attempts to introduce consistent HIV screening. Minimum standards for a BTS have been defined as: the capability to ensure that transfused blood is (a) grouped according to ABO-group and Rhesus factor, (b) cross-matched, (c) tested for common bloodborne infectious diseases of public health importance, (d) adequately recorded and (e) quality controlled'>. The value of introducing large scale HIV testing in the absence of these standards is doubtful. A successful integration of HIV ELISA screening therefore often necessitates upgrading of existing services. In intermediate situations, where these minimum requirements are not met, there is nevertheless a need for some form of HIV screening of donor blood. The emergence of a new generation of rapid agglutination tests, some of which can be considered true field tests and can be performed on a one-off basis, allows testing of collected units of blood, even in the absence of a comprehensive blood transfusion

22 service. The introduction of such tests greatly increases the potential for HIV screening in peripheral centres, in countries where warm donations are the rule and not the exception. It is, however, clear that the possibilities for quality control are limited in such a situation, and in the longer term the development of a regular BTS should be foreseen. The value of blood screening will have to be reassessed when an HIV vaccine becomes available. Such a vaccine will render people who are HIV uninfected HIV antibody positive. Screening of blood will then have to rely on an antibody that distinguishes between HIV infection and vaccination, or will have to make use of an antigen detection test. (3) CONTROL OF THE CLINICAL USE OF BLOOD

A careful evaluation (audit) of current clinical practice, in particular of the indications for which blood transfusion is ordered, may reveal a potential for considerable reduction in the use of blood and blood products. Teaching 'transfusion medicine' to physicians and medical students would allow optimal use of blood and blood products. Such teaching should emphasize correct indications for transfusion; national guidelines should be developed and adhered to. Both evaluation and teaching should deal also with the use of alternatives to blood transfusion, including plasma substitutes and safe plasma proteins. In a number of cases the use of normal saline or plasma expanders would obviate the need for potentially contaminated blood. It is often assumed that the cost of such substitutes, usually purchased with scarce foreign currency, is prohibitive. An underlying assumption is that blood on the contrary is more or less free of charge, it has been shown in Table 1 that this is not the case. The cost of a unit of normal saline purchased in Europe and shipped to sub-Saharan Africa is approximately US$ 1.50, while the cost of a unit of dextran is about US$5.OO 14 • This compares favourably with the cost of blood. Possibilities for the local production of saline and plasma expanders should be explored and this capability should be developed where possible. For a small number of indications, mostly related to cold surgery, and in well-established blood transfusion services, autologous transfusion is an acceptable alternative to the transfusion of donated blood.

Tropical Doctor, January 1992 (4) TREATMENT OF BLOOD PRODUCTS TO MAKE THEM SAFE

Some blood products (not, unfortunately, whole blood or red cells) can be treated in such a way that viruses are destroyed or separated from the final product. Heat treatment in liquid phase of Factor VIII is an example of a successful intervention. Alcohol fractionation technique, which is used in the production of intramuscular gammaglobulin and albumin, was in use before the HIV epidemic and effectively eliminates HIV and other viruses. Betaproprionolactone with ultraviolet irradiation, dry heating at 80°C for 72 h and solvent detergent treatment are efficient techniques to destroy all known virus in plasma products'

The provision of safe blood--policy issues in the prevention of human immunodeficiency virus transmission.

The AIDS epidemic has focused attention on the constraints and deficiencies present in many blood transfusion services in the developing world. We dis...
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