NEW YORK (GenomeWeb) – The US Centers for Disease Control and Prevention has published data from Puerto Rico regarding the use of an investigational PCR-based blood-screening Zika test from Roche to demonstrate that infection rates are increasing.
During a telebriefing this morning to provide an update on screening of blood donations for Zika virus, Matthew Kuehnert, director of the agency's office of blood, organ, and other tissue safety, described the Roche Cobas test as "extremely accurate."
The test has not been granted Emergency Use Authorization as a diagnostic, but rather permitted for use under a contrasting regulatory category of Investigational New Drugs and Biologics.
Due to possible risk of Zika transmission via blood products, blood donations were halted in Puerto Rico in February and the island was instead sent blood products from the mainland US. The CDC then announced in March that the Roche test could be used under an investigational new drug (IND) application to screen donated blood in areas with active mosquito-borne transmission of Zika virus.
It has now been in use in Puerto Rico since April 3, according to CDC's Director, Tom Frieden.
A Morbidity and Mortality Weekly Report issued by the CDC today revealed the agency is using data from the Roche test to get a picture of the evolving Zika situation in Puerto Rico.
Although it is admittedly "not a field survey," the screening results indicate "a steady increase in infections in blood donors in Puerto Rico," Frieden said.
The highest rate thus far is the one most recently reported. At just over 1 percent, it may extrapolate to about a 3 percent incidence rate in the general population, Frieden said. Overall, 68 out of 12,777 donations have tested positive to date.
The rate is on par with that from the first year of chikungunya transmission in Puerto Rico, Frieden noted, which ultimately saw one quarter of the population contracting the mosquito-borne virus. However, chikungunya is more likely to be symptomatic and quite painful, while four out of five cases of Zika do not show symptoms, making questionnaire-based screening less likely to be successful.
The CDC also began reporting adverse pregnancy outcomes related to Zika infection in the mainland US this week, and will begin reporting pregnancy statistics from Puerto Rico next week, Frieden said. So far, 1,386 locally acquired cases have been reported there among a population of about 3.7 million. Based on current information it is now "possible that thousands of pregnant women may become infected" as the year progresses, Frieden added.
Frieden emphasized during the briefing that there have been no locally acquired Zika cases in mainland US and that blood centers are currently guided to exclude donors who have traveled to, or had sexual contact with anyone who has traveled to, Zika-affected areas.
While the IND authorizes the test to be used in Zika-affected areas, Frieden said that if a mainland US "blood center elects to test using the Roche assay, they are free to do so."
The Roche screening test is currently being used by at least one mainland donation center — Gulf Coast Regional Blood Center, "the primary supplier of blood components to more than 170 hospitals and health care facilities in a 26-county Texas Gulf Coast region," according to its website. The Center released a statement on May 23 announcing that it would be bringing on the Roche screening assay. Due to the test being in a trial stage, all donors must sign a consent form in order for the test to be administered to their blood, the Center said.
Gulf Coast Regional Blood Center has now tested more than 9,000 donations with the Roche test and did not have a single positive result so far, CDC's Kuehnert noted. This led him to the conclusion that there were no false-positive tests either, suggesting the test is highly accurate, he added.
Regarding false-negative tests, he said: "This test is very, very sensitive ... Analyses show the test detects a few copies of virus per milliliter of blood, so it is very unlikely that a donor with Zika infection is going to be missed through screening."
The agency representatives deferred to Roche or specific blood centers to detail the exact cost of the screening, but estimated it is a few dollars per test. "If blood centers choose to test, and have a positive, they are instructed to inform state and local health agencies and the CDC," Kuehnert further said.
The agency's own Trioplex assay is less sensitive than the Roche test, Frieden said, and detects cases for a longer time after initial infection using urine as a sample type, leading to the recent guideline update for paired urine and blood testing. He also suggested the agency might be tweaking its test in the future to improve sensitivity. In addition to the Trioplex, PCR-based Zika assays from Quest Diagnostics and Altona Diagnostics are currently authorized under EUA.
The Roche Cobas system is also one of two that could be used for "triplex" testing for HIV, and hepatitis B and C viruses by the American Red Cross. That blood donation group currently uses the Procleix Ultrio Plus from Hologic but reevaluates every few years, as previously reported. Roche has won major blood screening tender contracts in Thailand, Germany, the UK, and Spain, which involve the Cobas 6800 and Cobas 8800 systems, the firm stated in a recent earnings call.