CORRECTED-Hepatitis C core antigen tests accurately diagnose HCV infection

Last Updated: 2016-06-29

(Changes "he" to "she" in para 9.)

By Will Boggs MD

NEW YORK (Reuters Health) - Several hepatitis C virus core antigen (HCVcAg) tests accurately diagnose hepatitis C virus (HCV) infection and could replace nucleic acid testing (NAT) in settings where HCV is prevalent, according to a systematic review and meta-analysis.

"Overall, several of the tests perform very well and while they are not equal to NAT, the lower costs may improve diagnostic capacity in the appropriate setting," Dr. J. Morgan Freiman from Boston Medical Center in Massachusetts told Reuters Health by email.

The current two-step diagnostic procedure for diagnosing HCV infection -- screening for antibodies to HCV followed by NAT for those with anti-HCV antibodies -- is a major bottleneck for addressing the HCV elimination strategy proposed by the World Health Organization. Currently, there are five tests for HCVcAg commercially available.

Dr. Freiman and colleagues evaluated the accuracy of diagnosis of active HCV infection among adults and children for these five commercially available tests compared with NAT in their systematic review and meta-analysis of 44 published reports.

The pooled sensitivity and specificity were 93.4% and 98.8% for the Abbott ARCHITECT assay, 93.2% and 99.2% for the Ortho HCV Ag ELISA, and 59.5% and 82.9% for the Hunan Jynda HCV Ag ELISA. There was insufficient information for a pooled analysis of the Eiken Lumispot HCV Ag and the Fujirebio Lumipulse Ortho HCV Ag assays.

Three reports showed that the HCVcAg correlated well with RNA when levels were at least 3000 IU/mL when the Abbott ARCHITECT assay was used, according to the June 21 Annals of Internal Medicine report.

"Although even tests with the highest performance are not as sensitive as NAT, well-performing HCVcAg tests with an analytic sensitivity reaching into the femtomolar range (equal to 3000 IU/mL) could replace NAT for HCV detection, particularly if a lower cost per test allows more patients to be served," the researchers conclude. "Therefore, HCVcAg should be explored for point-of-care (POC) testing to increase the number of patients diagnosed and streamline the HCV cascade of care."

"There is much more work to be done to determine at what sensitivity threshold a POC test would be clinically useful," Dr. Freiman said. "In settings with reliable access to centralized laboratory processing and higher diagnostic capacity, a POC test may still prove to be useful as a screening tool, but would be less likely to replace confirmatory nucleic acid testing (NAT)."

"We have the technology to detect circulating HCV RNA down to 15 IU/mL - amazing -- but how clinically relevant is that threshold when access to testing is equally as important as accuracy in resource limited settings?" she wondered.

Dr. Jose-Manuel Echevarria, from Carlos III Health Institute, Madrid, Spain, who recently reported that HCV core-specific antibody may represent occult HCV infection among blood donors, told Reuters Health by email, "Physicians should conclude from the report that HCVcAg testing provides trustful diagnostic results for the characterization of their anti-HCV positive patients as viremic or non-viremic before deciding about antiviral treatment."

"I would add that HCVcAg testing is particularly useful for the purpose of transfusion centers," he said. "Chronically infected blood donors are detected by anti-HCV screening, and HCVcAg will detect efficiently almost every blood unit obtained from donors experiencing the window period of the acute HCV infection, who test negative for anti-HCV."

"At present, high-resource settings will for sure use NAT testing because of its higher sensitivity, and because automatic equipment has reduced the chance for false-positive results because sample-to-sample contamination (is kept) to a minimum," Dr. Echevarria concluded. "However, HCVcAg testing is extremely useful and convenient for low-resource settings, and also for emergency units everywhere."

The National Institutes of Health funded this research. Three coauthors reported disclosures.

SOURCE: http://bit.ly/28LpRcU

Ann Intern Med 2016.