Varicella-Zoster Virus Testing in Clinical Practice in the U.S., 2016-2023

Varicella-zoster virus testing is increasingly needed for assessing immunity and diagnosis in the varicella vaccination era. Varicella-zoster virus-specific immunoglobulin G (IgG) is recommended when assessing immunity; real-time polymerase chain reaction (PCR) is recommended for varicella or herpes zoster diagnosis. The study objective was to describe varicella-zoster virus serologic and virologic testing in U.S. clinical practice.

Patients with serologic (IgG, immunoglobulin M [IgM]) or virologic (PCR, culture) varicella-zoster virus testing were identified in five administrative data sources (∼11-100 million enrollees; 2016-2023). Descriptive analyses were used to examine varicella-zoster virus testing frequency, patient characteristics, and rates by test type. The top 20 diagnostic codes associated with varicella-zoster test type were used as a proxy for reason for testing.

Across data sources, the highest proportion of varicella-zoster virus testing was for IgG (43%-92%); most was in females (79%-82%) and those aged 20-39 years (62%-70%). Rates of serologic testing were 50-60/10,000 persons. Frequency of varicella-zoster virologic testing was considerably lower; PCR testing rates were ∼1/10,000 persons. Diagnostic codes associated with IgG or virologic testing were primarily categorized as routine care or acute illness, respectively. IgM testing was up to 11% of tests, despite not being recommended for screening or diagnostic purposes.

Varicella-zoster virus serologic testing rates were 50-60 times higher than PCR. Serologic testing was more common among females and young adults, likely due to screening. Most varicella-zoster virus testing appeared relevant to clinical management; however, inappropriate IgM testing was identified. Appropriate testing is important to guide clinical and public health management for varicella and herpes zoster.