Microscopy Quality Control in Médecins Sans Frontières Programs in Resource-Limited Settings

Derryck Klarkowski and Daniel Orozco describe the Médecins Sans Frontières program for monitoring the quality of microscopy for malaria, pulmonary tuberculosis, and leishmaniasis

The Evaluation of a Rapid In Situ HIV Confirmation Test in a Programme with a High Failure Rate of the WHO HIV Two-Test Diagnostic Algorithm

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

Percentage of laboratories and test centers achieving ≤5% false-positive and false-negative results for AFB microscopy.

<p>Percentage of laboratories and test centers achieving ≤5% false-positive and false-negative results for AFB microscopy.</p

Percentage of laboratories and test centers achieving ≤5% false-positive and false-negative results for malaria microscopy.

<p>Percentage of laboratories and test centers achieving ≤5% false-positive and false-negative results for malaria microscopy.</p

Percentage of laboratories and test centers achieving ≥95% agreement for malaria and AFB microscopy.

<p>Percentage of laboratories and test centers achieving ≥95% agreement for malaria and AFB microscopy.</p

Performance of malaria and AFB microscopy.

<p>Malaria microscopy for parasite detection, not species differentiation.</p><p>CI, confidence interval.</p

Analysis of double-positive rapid test results by enzyme immunoassay (OIC-HIV) and western blot (WB) banding pattern

<p>D+^s =  Determine HIV-1/2® strong-positive. D+^w =  Determine HIV-1/2® weak-positive. U+^s =  UniGold HIV® strong-positive. U+^w =  UniGold HIV® weak-positive. POS = positive. NEG =  negative. IND =  indeterminate.</p>1<p>The discrepancy between banding patterns in OIC-HIV and WB may have been caused by either laboratory/clerical error, or different patterns of cross-reactivity between the two tests.</p>2<p>Using Centers for Disease Control criteria <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0004351#pone.0004351-Centers1" target="_blank">[13]</a>.</p>3<p>Using the manufacturer's interpretation.</p

HIV Testing flowchart.

<p>HIV Testing flowchart.</p

Causes of false-positive HIV rapid diagnostic test results

HIV rapid diagnostic tests have enabled widespread implementation of HIV programs in resource-limited settings. If the tests used in the diagnostic algorithm are susceptible to the same cause for false positivity, a false-positive diagnosis may result in devastating consequences. In resource-limited settings, the lack of routine confirmatory testing, compounded by incorrect interpretation of weak positive test lines and use of tie-breaker algorithms, can leave a false-positive diagnosis undetected. We propose that heightened CD5+ and early B-lymphocyte response polyclonal cross-reactivity are a major cause of HIV false positivity in certain settings; thus, test performance may vary significantly in different geographical areas and populations. There is an urgent need for policy makers to recognize that HIV rapid diagnostic tests are screening tests and mandate confirmatory testing before reporting an HIV-positive result. In addition, weak positive results should not be recognized as valid except in the screening of blood donors