Investigation of a measles outbreak in Zimbabwe, 2010: potential of a point of care test to replace laboratory confirmation of suspected cases.

Blood and oral fluid (OF) samples were collected from 103 suspected measles cases between February and November 2010 during a nationwide measles outbreak in Zimbabwe. Siemens measles IgM enzyme immunoassay (EIA) on serum, Microimmune measles IgM capture EIA on OF, real-time haemagglutinin (H) gene PCR and nested nucleocapsid (N) gene PCR on OF were performed, confirming 75 measles cases. These samples were then used to evaluate a newly developed point of care test (POCT) for measles and determine its potential for identifying measles cases in outbreaks. After performing POCTs on OF samples, nucleic acid was extracted from the used test strips and the measles H and N genes amplified by RT-PCR. The sensitivity, specificity, positive and negative predictive values of the POCT for IgM in OF was 75·0% [95% confidence interval (CI) 63·4-84·5], 96·2% (95% CI 80·4-99·9), 98·2% (95% CI 90·3-100) and 58·1% (95% CI 42·1-73·0), respectively. The N gene sequences showed high level of agreement between original OF and corresponding POCT strips. Measles genotype B3 was identified in all cases. We conclude that the measles POCT has the potential to be used, at the point of contact, in outbreak situations and provide molecular characterization of the virus at a later date.

Diagnostic accuracy of commercial urinary lipoarabinomannan detection in African tuberculosis suspects and patients.

OBJECTIVE: To evaluate a commercially available antigen capture enzyme-linked immunosorbent assay (ELISA) based on detecting lipoarabinomannan (LAM) in urine for the diagnosis of tuberculosis (TB). DESIGN: Consenting TB suspects and registering TB patients prospectively recruited from three hospitals were asked for two sputum specimens for microscopy and culture, urine for LAM testing and blood for human immunodeficiency virus (HIV) testing, with radiological and clinical follow-up for 2 months. RESULTS: Of 427 participants, complete data were available from 397 (307 adult and 23 adolescent TB suspects, and 67 registering TB patients). HIV prevalence was 77%. TB was diagnosed in 195 (49%), including 161 culture-positive patients, and confidently excluded in 114 (29%) participants. LAM ELISA sensitivity was 44% (95%CI 36-52) for culture-confirmed TB (52% in smear-positive patients). Specificity was 89% (95%CI 81-94). Sensitivity was significantly higher in HIV-related TB (52%, 95%CI 43-62, P < 0.001) compared to HIV-negative TB (21%, 95%CI 9-37). Sensitivity in smear-negative patients was low (28%, 95%CI 13-43) for combined HIV-positive and -negative patients. CONCLUSION: Our findings confirm greater sensitivity of urine LAM detection for HIV-related TB. However, both sensitivity and specificity were suboptimal, suggesting that this version cannot confirm or exclude TB in either HIV-infected or non-infected patients.