Search

We report below an in vivo antimalarial efficacy study conducted in 2002 in Bundi Bugyo, a district of western Uganda housing a large displaced population. We tested sulfadoxine-pyrimethamine (SP), amodiaquine (AQ) and the combination chloroquine plus SP (CQ + SP). A total of 268 children with uncomplicated Plasmodium falciparum malaria were followed-up for 28 days according to WHO recommendations, with PCR genotyping to distinguish late recrudescences from re-infections. PCR-adjusted failure proportions at day 28 were 37.0% (34/92, 95% CI 27.1-47.7) in the SP group, 20.6% (14/68, 95% CI 11.7-32.1) in the AQ group and 22.8% (18/79, 95% CI 14.1-33.6) in the CQ + SP group. Early failures were particularly frequent in the SP group (15.2%). Clearance of gametocytes was slower in the SP and CQ + SP groups than in the AQ group. This study suggests that, in Bundi Bugyo, CQ + SP (Uganda's first-line regimen) will need to be replaced by a more efficacious regimen. Across Uganda, the deployment of SP containing combinations may not be a feasible long-term strategy. For Bundi Bugyo, we recommend a combination of artesunate and AQ. Our study also confirms previous findings that resistance is considerably underestimated by 14-day follow-ups. Antimalarial policy decisions should therefore be based on 28-day studies, with PCR adjustment to distinguish re-infections.

Background: The test menus for developed and developing countries may differ, depending on many factors, including the expected volume of testing, disease frequency and therapies available, clinical impact of the test, technical skill and equipment needed, cost, the patient population served, and whether alternative testing sites are available, and some of them may not be exactly known. We assessed test priorities in a developing country by making a broad range of tests available and then assessing which tests were actually used by the physicians in the country for the care of their patients. Methods: The Barnes-Jewish Hospital laboratory and Washington University Medical Center provided patients in the developing country of Eritrea access to the same tests as patients in St. Louis for all analytes that are stable at 4 °C, the lowest temperature that could be used for shipping. Results: The use of the St. Louis laboratories increased steadily from 1998 to 2001. More than one-half of the physicians in Eritrea used the reference laboratories, with requests for thyroid function and female fertility representing 48–71% of the test requests over the 4 years evaluated. The high degree of utilization for these test batteries was not predicted. Testing for thyroid function, female fertility, and lipid panels are now performed, or soon will be performed, in Eritrea based on the experience of the reference laboratory system. The reference laboratory system is continuing so that the test priorities of the country can be evaluated on an ongoing basis and specialized tests can be made available at a low cost. Conclusion: The experiences of a reference laboratory for a developing country can help to identify unanticipated priorities for medical testing within the country.

BACKGROUND: Current WHO testing guidelines for resource limited settings diagnose HIV on the basis of screening tests without a confirmation test due to cost constraints. This leads to a potential risk of false positive HIV diagnosis. In this paper, we evaluate the dilution test, a novel method for confirmation testing, which is simple, rapid, and low cost. The principle of the dilution test is to alter the sensitivity of a rapid diagnostic test (RDT) by dilution of the sample, in order to screen out the cross reacting antibodies responsible for falsely positive RDT results. METHODS: Participants were recruited from two testing centres in Ethiopia where a tiebreaker algorithm using 3 different RDTs in series is used to diagnose HIV. All samples positive on the initial screening RDT and every 10th negative sample underwent testing with the gold standard and dilution test. Dilution testing was performed using Determine™ rapid diagnostic test at 6 different dilutions. Results were compared to the gold standard of Western Blot; where Western Blot was indeterminate, PCR testing determined the final result. RESULTS: 2895 samples were recruited to the study. 247 were positive for a prevalence of 8.5 % (247/2895). A total of 495 samples underwent dilution testing. The RDT diagnostic algorithm misclassified 18 samples as positive. Dilution at the level of 1/160 was able to correctly identify all these 18 false positives, but at a cost of a single false negative result (sensitivity 99.6 %, 95 % CI 97.8-100; specificity 100 %, 95 % CI: 98.5-100). Concordance between the gold standard and the 1/160 dilution strength was 99.8 %. CONCLUSION: This study provides proof of concept for a new, low cost method of confirming HIV diagnosis in resource-limited settings. It has potential for use as a supplementary test in a confirmatory algorithm, whereby double positive RDT results undergo dilution testing, with positive results confirming HIV infection. Negative results require nucleic acid testing to rule out false negative results due to seroconversion or misclassification by the lower sensitivity dilution test. Further research is needed to determine if these results can be replicated in other settings. TRIAL REGISTRATION: ClinicalTrials.gov, NCT01716299 .

Background Recent trends to earlier access to anti-retroviral treatment underline the importance of accurate HIV diagnosis. The WHO HIV testing strategy recommends the use of two or three rapid diagnostic tests (RDTs) combined in an algorithm and assume a population is serologically stable over time. Yet RDTs are prone to cross reactivity which can lead to false positive or discordant results. This paper uses discordancy data from Medecins Sans Frontieres (MSF) programmes to test the hypothesis that the specificity of RDTs change over place and time. Methods Data was drawn from all MSF test centres in 2007-8 using a parallel testing algorithm. A Bayesian approach was used to derive estimates of disease prevalence, and of test sensitivity and specificity using the software WinBUGS. A comparison of models with different levels of complexity was performed to assess the evidence for changes in test characteristics by location and over time. Results 106, 035 individuals were included from 51 centres in 10 countries using 7 different RDTs. Discordancy patterns were found to vary by location and time. Model fit statistics confirmed this, with improved fit to the data when test specificity and sensitivity were allowed to vary by centre and over time. Two examples show evidence of variation in specificity between different testing locations within a single country. Finally, within a single test centre, variation in specificity was seen over time with one test becoming more specific and the other less specific. Conclusion This analysis demonstrates the variable specificity of multiple HIV RDTs over geographic location and time. This variability suggests that cross reactivity is occurring and indicates a higher than previously appreciated risk of false positive HIV results using the current WHO testing guidelines. Given the significant consequences of false HIV diagnosis, we suggest that current testing and evaluation strategies be reviewed.

BACKGROUND: Access to HIV diagnosis is life-saving; however the use of rapid diagnostic tests in combination is vulnerable to wrongly diagnosing HIV infection when both screening tests give a false positive result. Misclassification of HIV patients can also occur due to poor quality control, administrative errors and lack of supervision and training of staff. Médecins Sans Frontières discovered in 2004 that HIV negative individuals were enrolled in some HIV programmes. This paper describes the result of an audit of three sites to review testing practices, implement improved testing algorithms and offer re-testing to clients enrolled in the HIV clinic. FINDINGS: In the Democratic Republic of Congo (DRC), Burundi and Ethiopia patients were identified for HIV retesting. In total, 44 false-positive patients were identified in HIV programmes in DRC, two in Burundi and seven in Ethiopia. Some of those identified had been abandoned by partners or started on anti-retroviral therapy or prophylaxis. Despite potential damage to programme reputations, no impact in terms of testing uptake occurred with mean monthly testing volumes stable after introduction of re-testing. In order to prevent the problem, training, supervision and quality control of testing procedures were strengthened. A simple and feasible confirmation test was added to the test algorithm. Prevalence of false positives after introducing the changes varied from zero percent (95% CI 0%-8.2%) to 10.3 percent (95% CI: 7.2%-14.1%) in Burundi and DRC respectively. CONCLUSION: False HIV diagnoses were found in a variety of programme settings and had devastating individual consequences. We re-tested individuals in our programmes while instituting improved testing procedures without a negative impact on test uptake. Considering the importance of correct diagnosis to the individual, as well as the resources needed to care for someone with HIV, it is critical to ensure that all patients registered in HIV programmes are accurately diagnosed.

Derryck Klarkowski and Daniel Orozco describe the Medecins Sans Frontieres program for monitoring the quality of microscopy for malaria, pulmonary tuberculosis, and leishmaniasis.

Background Concerns about false-positive HIV results led to a review of testing procedures used in a Médecins Sans Frontières (MSF) HIV programme in Bukavu, eastern Democratic Republic of Congo. In addition to the WHO HIV rapid diagnostic test algorithm (RDT) (two positive RDTs alone for HIV diagnosis) used in voluntary counselling and testing (VCT) sites we evaluated in situ a practical field-based confirmation test against western blot WB. In addition, we aimed to determine the false-positive rate of the WHO two-test algorithm compared with our adapted protocol including confirmation testing, and whether weakly reactive compared with strongly reactive rapid test results were more likely to be false positives. Methodology/Principal Findings 2864 clients presenting to MSF VCT centres in Bukavu during January to May 2006 were tested using Determine HIV-1/2® and UniGold HIV® rapid tests in parallel by nurse counsellors. Plasma samples on 229 clients confirmed as double RDT positive by laboratory retesting were further tested using both WB and the Orgenics Immunocomb Combfirm® HIV confirmation test (OIC-HIV). Of these, 24 samples were negative or indeterminate by WB representing a false-positive rate of the WHO two-test algorithm of 10.5% (95%CI 6.6-15.2). 17 of the 229 samples were weakly positive on rapid testing and all were negative or indeterminate by WB. The false-positive rate fell to 3.3% (95%CI 1.3–6.7) when only strong-positive rapid test results were considered. Agreement between OIC-HIV and WB was 99.1% (95%CI 96.9–99.9%) with no false OIC-HIV positives if stringent criteria for positive OIC-HIV diagnoses were used. Conclusions The WHO HIV two-test diagnostic algorithm produced an unacceptably high level of false-positive diagnoses in our setting, especially if results were weakly positive. The most probable causes of the false-positive results were serological cross-reactivity or non-specific immune reactivity. Our findings show that the OIC-HIV confirmation test is practical and effective in field contexts. We propose that all double-positive HIV RDT samples should undergo further testing to confirm HIV seropositivity until the accuracy of the RDT testing algorithm has been established at programme level.

A group-and-screen system was introduced for selected surgical procedures to improve the cost-effectiveness of the hospital blood transfusion service. The mean crossmatch-transfusion ratio for eleven procedures was 11.1 but fell to 3.3 after the change. The overall crossmatch-transfusion ratio in the hospital improved from 2.7 to 2.2 (p No problems have arisen from the group-and-screen system to date. It has led to improvement in the efficiency and cost-effectiveness of the hospital blood bank and resulted in fresher blood being transfused.

A woman of 47 with lymphocytic lymphoma was found to have a high-titer cold autoagglutinin of anit-BI specificity. Her group B erythrocytes autoagglutinated of anti-BI specificity. Her group B erythrocytes autoagglutinated in vitro and the direct antiglobulin reaction was positive, but she had no symptom of cold intolerance, no evidence of hemolysis, and she could receive transfusions of compatible group O erythrocytes. In addition, evidence for synthesis of the autoantibody by the lymphoma cells was obtained by short-term bone-marrow culture.

The hospital blood bank plays a key role in the diagnosis of acute transfusion reactions involving red cell incompatibility. This paper discusses the interpretation of the serological tests performed by the laboratory. Because red cell incompatible transfusion reactions occur so infrequently it is difficult to accumulate practical experience in their laboratory presentation and this paper describes several of the pitfalls that may be encountered when laboratory findings deviate from classical descriptions. These include the absence of a positive direct antiglobulin test (Coombs) or an incompatible crossmatch, the absence of any apparent discrepancy between the pre- and posttransfusion specimens in cases of ABO incompatibility, the differentiation of auto-immune haemolytic anaemia from delayed transfusion reactions and the assessment of the clinical significance of any blood group antibodies that may be detected.

A successful bone marrow transplant results in chimerism, but various haematological markers are necessary to prove that a true chimera exists. Differences in the red cell antigens between the donor and the recipient of a bone marrow transplant provide ideal markers to confirm chimerism. In this paper, experience with the immunohaematological aspects of bone marrow transplantation will be discussed. It is now well established that red cell antigens, and in particular the ABO system, are not important in long-term marrow graft survival or graft versus host reaction. There are, however, practical considerations and difficulties in crossing the ABO barrier, and interesting immunohaematological questions are posed regarding tolerance and the nature of red cell antigens. Large volume plasma exchange with donor group fresh frozen plasma and infusion of A substance (when indicated) followed by a small transfusion of ABO incompatible red cells prior to marrow infusion, has been our standard approach to crossing the ABO barrier. In most cases, anti-A or anti-B isoagglutinins can be effectively reduced to undetectable levels and bone marrow infusion has been uneventful. In each case, anti-A or anti-B isoagglutinin titres have returned rapidly while awaiting engraftment, but have subsequently disappeared following marrow engraftment without clinical evidence of haemolysis. Haptoglobin levels have fallen to undetectable levels during this engraftment period, during which time mixed field ABO blood group reactions were present. IgG anti-A and anti-B have been present in most cases to high titre but have not been effectively removed by plasma exchange, However, in no case did the presence of IgG antibodies appear to be clinically significant. Some interesting changes in blood group antigens have been observed. In one case the emergence of the A 2 antigen clearly preceded the A 1 antigen in the transformation of 0 to A, and a second case of anti-A 1 developed in an A 1 to A 1 graft.

Background. World Health Organization guidelines now recommend routine use of viral load testing, where available, for patients receiving antiretroviral treatment (ART). However, its use has not been routinely implemented in many resource-limited settings due to cost, availability and accessibility. Viral load testing is complex, making its application in resource-limited settings challenging. We describe the issues encountered by Médecins Sans Frontières (MSF) when using routine viral load testing in a large HIV programme in sub-Saharan Africa. Methods Between October 2005 and August 2006, more than 1200 patients on ART had viral load tests at baseline and at three-month intervals performed by a local reference laboratory that was quality assured by an experienced international institution. Concerns with reliability of results halted testing. The quality control measures instituted with a second laboratory and outcomes of these were documented. Results In 2005 and 2006, only 178 of 334 (53%) previously ART-naïve patients tested after six to 12 months of treatment had viral loads of less than 1000 copies/mL. Similar MSF programmes elsewhere demonstrated virological suppression rates of more than 85%, and duplicate testing showed unacceptable discordance. Laboratory problems encountered included: disregarded quality control; time delays; requirement for retesting; and duplicate sample variations. Potentially harmful clinical outcomes of inaccurate viral load results include: unnecessary ART regimen changes; unnecessary enhanced adherence counselling after "false failures"; and undetected virological failure. Conclusions Viral load testing performed without rigorous quality control carries the risk of erroneous and potentially damaging results. Viral load testing should be utilized only if robust quality assurance has been implemented. Our experience in this and other settings led to the development of a guide for assessing the suitability of a laboratory for viral load testing that can be used to help achieve reliable results.