Repeat Molecular Testing for Respiratory Pathogens: Diagnostic Gain or Diminishing Returns?

Upper respiratory tract infections are common, and the ability to accurately and rapidly diagnose the causative pathogen has important implications for patient management.

We evaluated the test-ordering practices for 2 commonly utilized nucleic acid amplification tests (NAATs) for the detection of respiratory pathogens: the Xpert Flu Assay for influenza A/B (Flu assay) and the Biofire FilmArray respiratory panel assay (RP assay), which detects 20 different targets. Our study examined repeat testing; that is, testing within 7 days from an initial test.

Our study found that repeat testing is common for each of the individual assays: 3.0% of all Flu assays and 10.0% of all RP assays were repeat testing. Of repeat testing, 8/293 (2.7%) of repeat Flu assays and 75/1257 (6.0%) of RP assays resulted diagnostic gains, i.e., new detections. However, for the RP assay, these new detections were not always clinically actionable. The most frequently discrepant organisms were rhinovirus/enterovirus (28/102, 27.5%), followed by respiratory syncytial virus (12/102, 11.8%) and coronavirus OC43 (11/102, 10.8%). Furthermore, there were 3,336 instances in which a patient was tested using both a Flu assay and RP assay, of which only 44 (1.3%) had discrepant influenza results.

Our findings suggest opportunities exist to better guide ordering practices for respiratory pathogen testing, including limiting repeat testing, with the goal of optimization of clinical yield, and diagnostic stewardship.