Author response to "Poor specificity of urinary cryptococcal antigen testing".

Abstract

I thank the authors for raising the important issue of diagnostic accuracy of the lateral flow cryptococcal antigen (CrAg) assay for estimating cryptococcal antigenuria prevalence. In response to a disappointing diagnostic specificity when testing urine samples 1, the manufacturer (Immy Inc., Norman, OK, USA) developed a diluent specific for urine CrAg testing, which we used in our study. To my knowledge, there has only been one study reporting on the diagnostic accuracy of the lateral flow assay when using the manufacturer's diluent on urine samples. That study, conducted among HIV-infected adults with CD4 count < 200 cell/μL in Tanzania, reported a sensitivity of 80% and specificity of 92%, when compared to using the same lateral flow assay tested on serum samples 2. Because the Tanzanian study had only 10 CrAg-positive adults among 140 total participants and used the lateral flow assay as the gold standard diagnostic test, additional clinic-based diagnostic accuracy studies with a larger sample size and gold-standard latex agglutination testing are still needed. Regardless, cryptococcosis represents a significant burden of disease among HIV-infected adults in our study region, and clinic-based screening at initial HIV diagnosis may be an important intervention for diagnosing CrAg-positive individuals.