Clinical validity of enterovirus PCR testing of skin swabs samples

Enteroviruses cause a diverse spectrum of diseases. In 2018, enterovirus PCR was included in the standard panel of skin swabs investigations, which already included HSV and VZV. Here we show evidence that positive PCR results for enterovirus correlate with clinical data obtained through retrospective review.

Method:

A retrospective search of laboratory records for all skin swabs between July 18 and March 19 was performed. Enterovirus PCR positive results were correlated with clinical information from request forms and electronic patient records. A subset of positive samples was sent to the reference laboratory for genotyping by Sanger sequencing of the VP1 gene.

Of 1159 specimens tested, 108 were positive for enterovirus, 194 were positive for HSV 1, 70 for HSV 2, 167 for VZV. Median age for enterovirus positive patients was 1 year, compared with 29 years for HSV and VZV positive patients. 99 enterovirus positive results correlated clinically, 2 did not correlate, and 7 had no clinical information available. Those with clinical correlation had a higher PCR cycle threshold (CT), than those without (mean 27.4 vs. 38).

12 samples were sent to the reference laboratory. Of the 6 that could be successfully genotyped, all were Coxsackie A6.

Conclusions

Positive enterovirus PCR in skin swabs correlated well with clinical signs, demonstrating validity. The identification of Coxsackie A6 on all sub-typed isolates further supports the validity of a positive result, as does the younger median patient age for patients testing positive for enterovirus compared to other viral infections.