Hepatitis C Saliva Tests May Show a False-Negative Result if HIV Is Also Present

Although simple and convenient, saliva tests for hepatitis C infection may not be the best option for determining infection status, particularly in patients who may have a concurrent HIV infection.

According to the results of a study appearing in the July 2013 edition of Journal of Clinical Virology, the tests are a passable option for screening at-risk populations for the virus; however, the increased chance for a false-negative result when a patient also has an HIV infection severely limits the tests’ efficacy.

“Hepatitis C oral fluid antibody detection methods have great compliance levels, low cost, and authorise sampling in any place, without highly qualified personnel,” the authors noted. “Yet, HCV antibodies saliva detection methods present insufficient performances for the general population … The relative lack of sensitivity in the HIV infected population found in the present work is, however, a serious limitation as many HIV-infected persons are also HCV infected.”

The researchers used a modified serological assay protocol and compared the results to participants’ HIV serological status, CD4 cell counts, HIV viral loads, and HCV replication status. Researchers included 30 patients with HCV but not HIV, 28 patients without HIV or HCV, 30 patients with both HCV and HIV, and 30 patients with HIV but without HCV. Researchers used the Salivette kit, a saliva testing kit manufactured by Sarstedt LTD, to obtain saliva samples.

In the HIV-negative groups of participants, the anti-HCV antibody tests had 90% and 100% sensitivity and specificity. In participants with an HIV infection, the tests registered 93% specificity, and 73% sensitivity.

“A recent study on HCV rapid screening assays presented also [sic] higher rates of false-negative results on HIV-positive patients,” the authors noted. “This decreased sensitivity in HIV-infected patients could be linked to a lower concentration of HCV-antibody oral fluids when compared to a non—HIV-infected control population … The observed sharp drop from 90 to 73.3% of salivary testing sensitivity in the HIV population is in accordance with the 2 previous observations.”

In the 22 patients with an HIV viral load below 200 copies per milliliter, 19 tested positive for salivary HCV-AB, which amounted to an 86% sensitivity for salivary detection of anti-HCV antibodies. Despite this, the sensitivity dropped to 37.5% for 8 patients with HIV replication that ranged from 1830 to 166,000 copies per milliliter.

Researchers noted that the small number of participants in the cohort prevented them from having a cut-off value for the viral load analysis.

At the time of saliva collection, HCV replication status was available for 26 patients in the HIV-negative and HCV-positive cohort, and 28 patients in the HIV-positive and HCV-positive cohort. 95% of participants in the HIV-negative and HCV-positive were correctly identified as having HCV by the saliva test.

In the HIV-positive, HCV-positive cohort, however, only 80% were considered HCV positive according to the saliva test.

“Our study, in agreement with previous works, highlights the poor performances of such oral tests, particularly in co-infected patients,” the authors wrote. “Mostly, the poor sensitivity seems unacceptable and such tests should not be used even in populations with limited access to health care facilities. Alternatives do exist and may offer, through simple finger prick, a more reliable screening strategy.”