Drug & Device Development

Assay detects hepatitis C antibody in oral fluids, dried blood spots

Last Updated: 2003-09-01 8:15:37 -0400 (Reuters Health)

NEW YORK (Reuters Health) - A modified commercial assay accurately detects antibody to hepatitis C virus (HCV) in oral fluids and dried blood spots, according to a report in the September Journal of Medical Virology.

Collection of oral fluid in nonclinical locations and community settings is far more convenient than venous blood collection, the authors explain, but few studies have examined the sensitivity and specificity of assays and collection device combinations for anti-HCV antibodies in oral fluid.

Dr. Ali Judd from Imperial College London, UK, and associates evaluated the sensitivity and specificity of a modified commercial assay for testing for anti-HCV in oral fluid samples collected by OraSure and Salivette systems and in dried blood spots using samples from 394 HCV-negative blood donors and 253 HCV-positive clinic patients. The modified protocol "employed a reagent bank, triplicate tests of a negative control oral fluid, and duplicate tests of a positive control oral fluid," the authors write.

The authors found that the OraSure device has a 91.7% sensitivity and 99.2% specificity in a population whose anti-HCV prevalence ranges from 15% to 50% when an optical density (OD) cutoff value 2 standard deviations from the mean is used.

For the Salivette device, the report indicates, 74.1% sensitivity and 99% specificity are possible where the prevalence is 30%, whereas sensitivity rose to 82.5% and sensitivity fell to 92.8% if the prevalence estimate increased to 50% and the cutoff fell to 1 standard deviation from the mean OD.

Regardless of population prevalence estimates, dried blood spots yielded 99.6% sensitivity and 100% specificity, the researchers note.

"We show that collecting oral fluid, in particular using the OraSure device, is an acceptable and sufficiently accurate method for the surveillance of HCV among injecting drug users (as well as other populations)," the authors write.

"In addition," the investigators add, "dried blood spots may provide a superior alternative method of specimen collection among this group, with the sensitivity and specificity of the modified Ortho EIA method being close to 100%. This level of accuracy is adequate for use as a diagnostic test, particularly in hard-to-reach populations."

J Med Virol 2003;71:49-55.