Potential for false-positive HIV test results using rapid HIV testing algorithms

Background: In order to scale up access to HIV counselling and testing in Nigeria; an HIV diagnostic algorithm based on rapid testing was adopted. However; there was the need to further evaluate the testing strategy in order to better assess its performance; because of the potential for false positivity.Objectives: The objective of this study was to compare positive HIV test results obtained from the approved rapid testing algorithm with results from western blot tests performed on samples from the same patient.Methodology: A retrospective review was conducted of HIV screening and confirmatory results for patients seen between 2007 and 2008. Rapid test and western blot results were extracted and compared for concordance. Discordant results were further reviewed using a combination of HIV-1 RNA viral load and CD4+ cell count test results and clinical presentation from medical records. Results: Analysis of 2228 western blot results showed that 98.3% (n = 2191) were positive for HIV-1; 0.4% (n = 8) were positive for HIV-2 and 0.3% (n = 7) were dual infections (positive for both HIV-1 and HIV-2); 0.6% (n = 13) were indeterminate and 0.4% (n = 9) were negative. Further investigation of the 13 indeterminate results showed nine to be HIV-1 positive and four to be HIV-negative; for a total of 13 negative results. The positive predictive value of the HIV counselling and testing algorithm was 99.4%.Conclusion: Using the rapid testing algorithm alone; false positives were detected. Therefore; effective measures such as training and retraining of staff should be prioritised in order to minimise false-positive diagnoses and the associated potential for long-term psychological and financial impact on the patients

Potential for false-positive HIV test results using rapid HIV testing algorithms.

Background: In order to scale up access to HIV counselling and testing in Nigeria, an HIV diagnostic algorithm based on rapid testing was adopted. However, there was the need to further evaluate the testing strategy in order to better assess its performance, because of the potential for false positivity. Objectives: The objective of this study was to compare positive HIV test results obtained from the approved rapid testing algorithm with results from western blot tests performed on samples from the same patient. Methodology: A retrospective review was conducted of HIV screening and confirmatory results for patients seen between 2007 and 2008. Rapid test and western blot results were extracted and compared for concordance. Discordant results were further reviewed using a combination of HIV-1 RNA viral load and CD4+ cell count test results and clinical presentation from medical records. Results: Analysis of 2228 western blot results showed that 98.3% (n = 2191) were positive for HIV-1, 0.4% (n = 8) were positive for HIV-2 and 0.3% (n = 7) were dual infections (positive for both HIV-1 and HIV-2); 0.6% (n = 13) were indeterminate and 0.4% (n = 9) were negative. Further investigation of the 13 indeterminate results showed nine to be HIV-1 positive and four to be HIV-negative, for a total of 13 negative results. The positive predictive value of the HIV counselling and testing algorithm was 99.4%. Conclusion: Using the rapid testing algorithm alone, false positives were detected. Therefore, effective measures such as training and retraining of staff should be prioritised in order to minimise false-positive diagnoses and the associated potential for long-term psychological and financial impact on the patients.

Proficiency testing for HIV, tuberculosis and malaria diagnosis in clinical laboratories in Nigeria.

BACKGROUND: Proficiency testing (PT) is a means of verifying the reliability of laboratory results, but such programmes are not readily available to laboratories in developing countries. This project provided PT to laboratories in Nigeria. OBJECTIVES: To assess the proficiency of laboratories in the diagnosis of HIV, tuberculosis and malaria. METHODS: This was a prospective study carried out between 2009 and 2011. A structured questionnaire was administered to 106 randomly-selected laboratories. Forty-four indicated their interest in participation and were enrolled. Four rounds of pre-characterised plasma panels for HIV, sputum films for tuberculosis and blood films for malaria were distributed quarterly by courier over the course of one year. The results were returned within two weeks and scores of ≥ 80% were reported as satisfactory. Mentoring was offered after the first and second PT rounds. RESULTS: Average HIV PT scores increased from 74% to 95% from the first round to the third round, but decreased in the fourth round. For diagnosis of tuberculosis, average scores increased from 42% in the first round to 78% in the second round; but a decrease to 34% was observed in the fourth round. Malaria PT performance was 2% at first, but average scores increased between the second and fourth rounds, culminating in a fourth-round score of 39%. Many participants requested training and mentoring. CONCLUSIONS: There were gross deficiencies in the quality of laboratory services rendered across Nigeria. In-country PT programmes, implemented in conjunction with mentoring, will improve coverage and diagnosis of HIV, tuberculosis and malaria.

Prevalence and risk factors of asymptomatic bacteriuria among pregnant Nigerians infected with HIV.

OBJECTIVE: There are conflicting report on the association of HIV infection and asymptomatic bacteriuria (ASB). Most of these studies were from areas with low HIV burden. This study determined the prevalence and risk factors of ASB in HIV positive pregnant women. METHODS: A cross sectional study among HIV positive pregnant women seen at a large PMTCT clinic in Lagos Nigeria. The women were evaluated for ASB at first clinic attendance. Blood samples were also collected for viral load, CD4 count and hemoglobin levels assessment. Data were managed with SPSS for windows version 19. RESULTS: 102 (18.1%) women out of 563 studied were found positive for asymptomatic bacteriuria. Ninety-seven (95.1%) of the positive samples yielded single bacterial isolates. Escherichia coli (44.3%) and Proteus mirabilis (21.6%) were the most common bacterial isolates. Previous urinary tract infection (OR: 4.3), HIV-1 RNA greater than 10,000 copies/ml (OR: 3.9), CD4 count <200 cells/mm3 (OR: 1.4) and maternal hemoglobin <11 g/dl (OR: 1.4) were factors significantly associated with ASB after controlling for possible confounders. CONCLUSION: ASB is common in HIV positive pregnant women in our environment and is associated with previous UTI, high viral load, low CD4 count and maternal hemoglobin <11 g/dl.