Under-allocation: Critical Supply Chain Hurdles Negatively Impact the Ability of Community Hospitals To Perform Repeat SARS-CoV-2 Testing.

LETTER

There is increasing recognition that not all severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reverse transcription-PCR (RT-PCR) assays are created equal with respect to test performance (1). A recently published study found that 7.1% of COVID-19 patients with initially negative RT-PCR results had SARS-CoV-2 detected upon repeat testing (2). Infectious Disease Society of America (IDSA) guidelines advocate for repeating testing in patients with intermediate or high clinical suspicion of COVID-19 infection when the initial test is negative (https://www.idsociety.org/practice-guideline/covid-19-guideline-diagnostics/).

Adoption of this strategy in the United States is challenging in the setting of widespread shortages of nasopharyngeal (NP) swabs and testing reagents. Our own institutions have experienced such shortages, and repeat testing generally requires approval. We performed a retrospective chart review to assess the impact of a restrictive approach to retesting. Between March and mid-April 2020, 1,128 patients underwent testing for SARS-CoV-2 at our institutions, of whom 232 were positive with a single NP swab specimen (20.6%). Of the 896 patients with negative results, only 33 underwent repeat SARS-CoV-2 testing (3.7%), of whom only one (3.0% [1/33]) was positive. This patient was retested on a subsequent hospital admission for new onset of respiratory symptoms. Among 22 patients who underwent repeat testing during the same hospital admission (22/33), the median time to retesting was 3.1 days.

We acknowledge the possibility that others in our cohort may have been identified as positive had routine retesting been performed. IDSA guidelines suggest that testing of a second specimen is associated with a 17% increase in test sensitivity. Based on this, we estimate that routine repeat testing could have led to additional detections of 48 cases in our patient cohort.

IDSA guidelines recommend testing of lower respiratory tract specimens if the initial NP specimen is negative in patients with an intermediate or high suspicion of infection. However, the majority of commercial assays for SARS-CoV-2 detection are not cleared for such specimens, and testing is available only in some reference laboratories. Only three patients in our cohort had alternate specimen types tested for SARS-CoV-2 (one oropharyngeal swab, one tracheal aspirate, and one bronchoalveolar lavage sample), and all three were negative.

Supply chain issues have limited our capacity to test all patients whom we believe might actually have the infection despite an initially negative test result.

IDSA recommends repeat testing in certain clinical situations, and as the breadth of COVID-19 clinical presentations expands (3), every effort should be made to enable widely available testing in health care facilities. This will help ensure that all truly infected patients are not left undiagnosed and untreated, and will aid in avoiding unknown exposure to health care workers and other patients. In the meantime, our experience suggests that non-systematic repeat testing due to resource restrictions is unlikely to be fruitful.