Tuesday, May 10, 2016

MMWR: Interim Guidance for Zika Virus Testing of Urine — United States, 2016


The Zika virus is rarely delectable in blood serum more than a week after onset of symptoms, but in early 2015 we learned it can frequently be detected in the urine for  10 days or longer (see Jan 2015 EID Journal Detection of Zika Virus in Urine). 

More recent studies (see Fiocruz: Revisting Zika Virus Detection In Saliva & Urine and  Eurosurveillance: Prolonged Shedding Of Zika Virus RNA In Saliva - Italy) have hinted at and even longer detection window; two weeks or longer.

Today the CDC's MMWR has published new interim testing guidelines, along with a comparison of rRT-PCR testing of serum, saliva, and urine for the Zika virus. 

First stop, the new testing guidelines - which recommends serum and urine testing within the 1st 7 days of developing symptoms, and urine testing in the second week -  followed by a link and a summary from the test comparison report.

Diagnostic testing for Zika virus infection can be accomplished using molecular and serologic methods. Real-time reverse transcription–polymerase chain reaction (rRT-PCR) is the preferred test for Zika virus infection because it can be performed rapidly and is highly specific (1,2). However, in most patients, Zika virus RNA is unlikely to be detected in serum after the first week of illness (2,3). Recent reports using adaptations of previously published methods (2,4) suggest that Zika virus RNA can be detected in urine for at least 2 weeks after onset of symptoms (3,57).

Currently, the CDC Trioplex rRT-PCR assay is the only diagnostic tool authorized by the Food and Drug Administration for Zika virus testing of urine (1). Other laboratory-developed tests will need in-house validations to adequately characterize the performance of the assay and meet Clinical Laboratory Improvement Amendments requirements. Further investigation is needed to determine the sensitivity and utility of Zika virus rRT-PCR on urine specimens collected ≥14 days after onset of symptoms.

On the basis of the newly available data, CDC recommends that Zika virus rRT-PCR be performed on urine collected  < 14 days after onset of symptoms in patients with suspected Zika virus disease. Zika virus rRT-PCR testing of urine should be performed in conjunction with serum testing if using specimens collected < 7 days after symptom onset (8). A positive result in either specimen type provides evidence of Zika virus infection. Procedures for the collection and submission of body fluids, including urine specimens, have been described previously (9). CDC recommendations for Zika virus testing of serum and other clinical specimens remain unchanged at this time (8). CDC will continue to review and update guidance for Zika virus testing as new data become available.
I've only posted some brief excerpts, follow the link below to read the report in its entirety. 

Comparison of Test Results for Zika Virus RNA in Urine, Serum, and Saliva Specimens from Persons with Travel-Associated Zika Virus Disease — Florida, 2016
May 10, 2016
As of April 20, 2016, the Florida Department of Health Bureau of Public Health Laboratories (BPHL) tested specimens from 913 persons who met state criteria for Zika virus testing. On the basis of previous small case studies reporting real time reverse-transcription polymerase chain reaction detection of Zika virus RNA in urine, saliva, and semen, the BPHL collected multiple specimen types from persons with suspected Zika virus disease. BPHL testing results suggest urine might be the preferred specimen type to identify acute Zika virus disease.

What is already known about this topic?
Limited data suggest Zika virus is excreted in multiple body fluids, including urine and saliva. Urine and saliva might be appropriate specimens for evaluating Zika virus disease.

What is added by this report?
A comparison of reverse-transcription polymerase chain reaction (RT-PCR) test results for urine and serum specimens from 66 persons with Zika virus disease with both specimens collected on the same date indicated that approximately twice as many urine specimens (61) than serum specimens (31) tested positive. No results from RT-PCR testing of serum specimens were positive >5 days after symptom onset; results from testing nine of 11 urine specimens were positive. A further comparison of 53 persons with Zika virus disease with urine, saliva, and serum specimens collected on the same date found positive results from testing in 49 (92%) urine specimens, 43 (81%) saliva specimens, and 27 (51%) serum specimens.

What are the implications for public health practice?
 These results suggest urine might be a useful specimen for identifying acute Zika virus disease.