Comparative evaluation of validity and cost-benefit analysis of rapid diagnostic test (RDT) kits in diagnosis of dengue infection using composite reference criteria: A cross-sectional study from south India.

BACKGROUND & OBJECTIVES: Rapid diagnostic test (RDT) kits are widely used in India for the diagnosis of dengue infection. It is important to evaluate the validity and reliability of these RDTs. The study was aimed to determine the sensitivity, specificity and predictive value of four commercially available RDTs [Panbio Dengue Duo cassette, Standard Diagnostics (SD) Bioline Dengue Duo, J. Mitra Dengue Day-1 test and Reckon Dengue IgG/IgM] against composite reference criteria (CRC), and compare the cost of the tests. METHODS: In this prospective observational study for diagnostic accuracy, we tested stored blood samples from 132 cases of dengue and 149 controls of other infections as classified based on CRC, with all the four RDTs. The CRC was based on the epidemiological considerations, common clinical features and laboratory abnormalities. The non-dengue controls were the cases of proven alternative diagnosis. The diagnostic performances of the tests were compared in terms of sensitivity, specificity and predictive value along with the cost involved per test. RESULTS: The sensitivity of the Panbio and SD RDT kits was found to be 97.7 and 64.3% respectively, and the specificities were 87.8 and 96.6% respectively. The sensitivity of the NS1 antigen capture by SD Duo, Reckon, J. Mitra RDTs was 20.9, 18.6 and 27.1% respectively. The prevalence of dengue specific IgG antibody with Panbio RDT kits was 49.3%. The cost per test for Panbio, SD, Reckon and J. Mitra is US$ 6.90, 4.27, 3.29 and 3.61 respectively. CONCLUSION: It was concluded that in dengue outbreak, Panbio IgM capture RDT alone is reliable and easily available test which can be used in acute phase of dengue infection in any resource limited set up. NS1 capture rates by any of the other three RDTs might not be reliable for the diagnosis of acute dengue infection.

Renal tubular dysfunction associated with tenofovir therapy.

OBJECTIVE: To describe the i ncidence a nd cha racteristics of Tenofovir (TDF) induced nephrotoxicity among people living with HIV AIDS (PLHA) receiving TDF based anti-retroviral therapy (ART) at Christian Medical College, Vellore. METHOD: Medical record review of all the PLHA who is being enrolled and followed up at the ART clinic at CMC, Vellore. RESULTS: From 2006-11, a total of 274 PLHA have been initiated on TDF based ART. 10 (3.6%) patients developed TDF induced renal dysfunction after a mean duration of 42.6 (SD 19.5) months. 5 patients were female. At the time of initiation of TDF, the mean age was 41.2 (SD 6.1) years and CD4 T-cell count was 281.2 (SD 241.3) cells/µL. 9 patients were started on an NNRTI-based regimen, while only 1 was on a Pl/r-based regimen. 5 patients were asymptomatic. Out of the 5 symptomatic patients, 3 patients complained of anorexia and tiredness only; 1 patient had bone pains and proximal pelvic girdle muscle weakness only while 1 patient had both anorexia and proximal pelvic girdle muscle weakness. Urine examination of 8 patients (all symptomatic and 4 asymptomatic patients) revealed proteinuria on urine dip stick assay (1+ to 3+) without active sediments. 9 patients had decline in the estimated creatinine clearance from mean of 84.1 (SD 21.0) to 62.1 (SD 26.3) mL/min/1.73 m2. The mean plasma phosphate level was 2.08 (SD 0.45) mg/ dL. The mean alkaline phosphatase level increased from 130.7 to 290.8 U/L. Seven patients had features of Fanconi syndrome. All symptomatic patients showed clinical improvement within 2-7 months of discontinuation ofTDF and supplementation of phosphate and calcium. CONCLUSION: TDF-associated renal dysfunction has a long incubation period during which the patients are largely asymptomatic and reversible. Hence laboratory confirmation is essential with creatinine clearance, urine examination, and phosphate levels. Prompt change of TDF leads to almost complete resolution of the tubular dysfunction.