October 15, 2012

Rapid Tests Accurate in First-Line HCV Screening

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Courtesy US. Dept of Veterans Affairs

By: JENNIE SMITH, Family Practice News Digital Network

FROM ANNALS OF INTERNAL MEDICINE

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Major Finding: Blood-based point-of-care tests for hepatitis C virus have the highest sensitivity for screening at 98.9%, with specificity ranging from 99.5% for whole blood and 99.7% for serum or plasma.

Data Source: A meta-analysis of 18 studies that evaluated the accuracy of one or more tests.

Disclosures: Ms. Shivkumar and colleagues’ study was supported by grants from the Canadian Institutes of Health Research. None of the authors declared conflicts of interest.

Rapid diagnostic and point-of-care tests for hepatitis C virus are accurate enough to be used in first-line HCV screening worldwide, according to results from the first systematic review of evidence on such tests.

Blood-based point-of-care tests (POCTs) had better sensitivity and specificity overall than did blood-based rapid diagnostic tests (RDTs), Sushmita Shivkumar of McGill University, Montreal, Quebec, and her colleagues reported Oct. 15 in Annals of Internal Medicine.

POCTs do not require sample processing or refrigeration, and have a shelf life of 6 months or more. Rapid diagnostic tests, or RDTs, require refrigeration and sample processing. Manufactured by a variety of firms under various marketing names, all the tests can detect HCV infection in under 30 minutes, with many taking less than 5 minutes, according to the investigators, who conducted a meta-analysis of 18 studies evaluating the accuracy of one or more RDT or POCT, compared with standard assays (Ann. Intern. Med. 2012;157:558-566).

Ms. Shivkumar and her colleagues found blood-based POCTs (using serum, plasma, or whole blood) to be the most accurate of the tests evaluated in the included studies, showing 98.9% sensitivity with a 95% confidence interval [CI] of 94.5% to 99.8% for whole blood and 96.8% to 99.6% for serum or plasma). RDTs of serum or plasma had 98.4% sensitivity (95% CI 88.9% to 99.8%). Specificity was highest in POCTs of serum or plasma at 99.7% (95% CI, 99.3% to 99.9%), followed by POCTs of whole blood at 99.5% (95% CI, 97.5% to 99.9%), RDTs of serum or plasma at 98.6% (95% CI, 94.9% to 99.6%). POCTs for oral fluids had a sensitivity of 97.1% (95% CI, 94.7% to 98.4%) and specificity of 98.2% (95% CI, 92.2% to 99.6%).

POCTs and RDTs cannot distinguish between acute and chronic HCV infections, which is one of the reasons that public health organizations continue to favor conventional assays. The Food and Drug Administration currently approves the use of a single POCT for HCV, and for use only in nontraditional settings; in the United Kingdom and Canada such tests have not yet been approved.

However, by being fast, accurate, and cheaper than conventional tests, the rapid diagnostic and point-of-care tests offer "great potential for expanded first-line screening for hepatitis C infection and demonstrate the utility of blood-based singleton POCTs and of multiplex POCTs designed to provide integrated HIV and HCV screening of at-risk populations," Ms. Shivkumar and her associates wrote in their analysis. "Their rapid turnaround time limits loss to follow-up and facilitates early linkages."

The authors also concluded that their findings showed that the rapid and point-of-care tests could play a "substantial role" in expanded global screening initiatives for HCV.

The blood-based POCTs, besides being the most accurate, have the advantage of not requiring refrigeration, the investigators wrote. This feature is key in developing countries in Africa and Asia, where prevalence of HCV infection is highest.

Ms. Shivkumar and her colleagues noted several weaknesses in their meta-analysis, mostly related to the quality of studies included. Only three of the studies they evaluated were blinded, while four received industry funding; the conventional assays used as reference varied in the studies, and HCV genotype information was not collected in most.

The study was supported by grants from the Canadian Institutes of Health Research. None of the authors declared conflicts of interest.


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Tests Can Get More Into Treatment

Chronic hepatitis C virus (HCV) infection is a common worldwide problem. It is estimated that 170 million people are afflicted. Unfortunately, the majority of infected people remain undiagnosed. In many parts of the world, patients do not have access to medical personnel or diagnostic testing so that the diagnosis of HCV can be made. For patients that do have access, standard testing for HCV is cumbersome and expensive, adding to the diagnostic burden and diminishing the opportunity for diagnosis. Even in the United States, it is estimated that the majority of people infected with HCV have not been diagnosed. These factors have provided the impetus to develop less cumbersome and inexpensive tests for HCV, with the hope that they could be implemented throughout the world to increase the number of patients diagnosed with HCV.

Although there have been numerous studies examining individual diagnostic tests for HCV, there has not been an exhaustive review of both rapid and point-of-care screening tests for HCV. Ms. Shivkumar and her associates performed a literature review and meta-analysis of 18 studies worldwide that use the tests to screen for HCV in adults. They assessed the studies for diagnostic accuracy variables including sensitivity, specificity, likelihood rates (LRs) and diagnostic odds ratios (DORs) for available rapid and point-of-care diagnostic tests.

The assessment indicates that point-of-care tests of blood (serum, plasma, or whole blood) have the highest accuracy, followed by rapid diagnostic tests of serum or plasma and then by point-of-care diagnostic tests of oral fluids. However, all tests showed excellent sensitivity, specificity, likelihood rates and diagnostic odds ratios.

Strategies to improve the identification of patients infected with HCV are changing. In fact, the Centers for Disease Control and Prevention recently updated screening guidelines, recommending that screening change from ineffective risk-factor based screening to age-based screening. Testing strategies are also a source of potential improvement. This comprehensive global review suggests that rapid diagnostic and point-of-care tests are useful as initial screening tests for HCV. Although potential biases inherent in retrospective meta-analysis reviews are discussed, the quality of the analysis is excellent and the conclusions are valid.

These diagnostic test results are available rapidly in the field, and thus are available at the point of care. The tests are also relatively inexpensive and are easy to perform. With more effective therapies for HCV in development, broadening the ability to diagnose HCV worldwide is increasingly important. Integration of these tests into the diagnostic algorithm for HCV offers a more effective screening strategy with subsequent diagnosis of more people infected with HCV worldwide.

Dr. Steven L. Flamm is a professor of gastroenterology, hepatology, and surgery at Northwestern University, Chicago. He has no disclosures.

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