Pathology/Lab Coding Alert

Understand protocols and coding pitfalls.

Travel-related Zika virus infections have cropped up in all but four states, according to the latest Centers for Disease Control and Prevention (CDC) statistics, but there are no confirmed cases of locally-acquired mosquito-born Zika in the U.S. — yet.

Because an infected individual can spread the disease through a mosquito vector or through sexual transmission, and because Zika infection can have dire health consequences, especially during pregnancy, the CDC and state health agencies are on the alert with new testing protocols. Read on to make sure you’re in-the-know about the latest algorithms for testing, interpretation, and diagnosis of Zika virus infection.

Basics: Zika is in the flavivirus group of RNA viruses that have a primary mode of transmission through mosquito or tick bites, according to Sarah Todt, RN, CPMA, CPC, CEDC, Director, Provider Education & Audit for LogixHealth, a national coding and billing company in, Bedford, Mass. Other flaviviral emerging diseases with similar presentations include dengue and Chikungunya. Symptoms of these infections are similar and include fever, rash, arthralgia, myalgia and headache, with Zika also frequently including conjunctivitis. Fetal microcephaly — characterized by an abnormally small head and brain damage — and Guillian-Barre syndrome have also been implicated with Zika virus, she adds.

Get Familiar With Available Tests

When a healthcare provider requests testing for Zika virus, two main types of tests can fit the bill — real-time polymerase chain reaction (RT-PCR) assay and IgM serology.

Two RT-PCR assays are available for specimens such as urine, serum, amniotic fluid, or cerebral spinal fluid (CSF):

• Trioplex RT-PCR Assay to detect dengue, chikungunya and Zika virus RNA: This single test can identify infection with any of the three listed flaviviruses. The CDC and labs that are part of a public health emergency, such as state health labs, perform this test. “The CDC can take weeks or months for the results,” cautions Peggy Slagle, CPC, coding and compliance manager for the department of pathology/microbiology at the University of Nebraska Medical Center in Omaha.
• Zika Virus RNA Qualitative Real-Time RT-PCR test from Quest Diagnostics’ subsidiary: 
  This test identifies only possible Zika infection, and is the first test to be available through commercial labs based on a US Food and Drug Administration (FDA) emergency use authorization.
  “The availability of our new molecular Zika test provides physicians broad access to a diagnostic tool for managing the Zika outbreak,” according to Rick Pesano, vice president of R&D for Quest Diagnostics in a statement.

Serology: Zika serology testing involves an enzyme-linked immunoassay (ELISA) method. Clinicians may submit a serum specimen to detect Zika virus IgM using this test. For IgM positive or equivocal samples, the CDC may perform a follow-up Plaque Reduction Neutralization Test (PRNT) for Zika and dengue virus total antibody.

Testing criteria: Clinicians may order tests for patients who meet the CDC Zika virus clinical criteria, such as exhibiting signs and symptoms of infection. Optimal testing time frames are up to seven days following symptom onset for RT-PCR testing, or seven to 14 days after symptom onset for IgM testing. Clinicians may also order testing for patients who meet the CDC Zika virus epidemiological criteria, such as history of travel at a time and geographic region that coincides with active Zika transmission, or asymptomatic pregnant women who meet the travel or other criteria, such as sexual contact with a man who meets the travel criteria. “A negative IgM test result 2-12 weeks after known exposure suggests that a recent Zika virus infection did not occur, which may obviate the need for serial ultrasounds,” according to the CDC.

Beware interpretation pitfalls: Because circulating Zika virus RNA decreases over time following symptom onset, an RT-PCR test taken too late may be negative even if the patient had a Zika virus infection. Serology testing should follow a negative RT-PCR test to see if the patient has developed antibodies indicative of a Zika infection. However, a patient may have a false positive Zika IgM test due to cross reactivity with other flaviviruses such as dengue, yellow fever, Japanese encephalitis, or West Nile virus. The lab may then perform PRNT to measure virus-specific neutralizing antibodies to Zika virus, but this test is also subject to cross-reactive flavivirus results.

Check Out Zika-Test Coding Options

Because CPT^® does not provide a specific code for Zika RT-PCR testing, the appropriate code for the test is 87798 (Infectious agent detection by nucleic acid [(DNA or RNA]), not otherwise specified; amplified probe technique, each organism). As more commercial labs begin to perform this test, you should be familiar with this code to describe the RT-PCR assay.

Similarly, CPT^® does not provide a specific code for a Zika antibody test, so the most appropriate code to describe the Zika IgM test is 86790 (Antibody; virus, not elsewhere specified). However, when the CDC performs the test, you’ll bill only the handling and processing fee (99001, Handling and/or conveyance of specimen for transfer from the patient in other than an office to a laboratory [distance may be indicated]).

Resources: You can read more about Zika virus at www.ama-assn.org/ama/pub/physician-resources/public-health/zika-resource-center.page and www.cdc.gov/zika/hc-providers/.