What steps have been taken to mitigate coronavirus disease 2019 (COVID-19) diagnostic test shortages?

Updated: Apr 02, 2021
  • Author: James J Dunn, PhD, D(ABMM), MT(ASCP); more...
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Answer

During the course of the pandemic, a number of laboratories have experienced shortages of one or more tests, consumables, or reagents necessary for SARS-CoV-2 testing. [45, 46] According to a survey, these shortages have limited testing in many laboratories to only about 43% of their maximum capacity, on average. [45] This reduction in capacity has impacted the ability of hospitals and labs to perform tests in accordance with IDSA guidelines regarding the repetition of initially negative tests for those patients with high clinical suspicion of COVID-19. [47]

Due to reagent shortages for SARS-CoV-2 RNA detection, many labs have considered pooling specimens for testing. Pooling of samples has been applied to surge testing and as part of epidemiologic surveillance for other respiratory viruses. [48] If the pool tests positive, the individual specimens that make up the pool must be tested individually. This strategy can be effective under two conditions. One is that there be a low community positivity rate or prevalence. If it is too high, every pool will contain a positive specimen, with reassessment needed to determine which one it is. This limits the potential reagent savings associated with pooling. The second condition is that the loss of sensitivity must not be too great with regard to the dilution of potentially positive specimens with negative specimens. If the loss of sensitivity is too high, the number of false negatives can impact patient care and management.

The number of specimens that can be pooled together will depend on the community prevalence and the loss of sensitivity of the assay. [49] Studies have shown that pooling of even a small number of individual specimens may result in 6-7% more false negatives. [50] In particular, pooling specimens appears to impact the sensitivity of detection in patients with low viral loads, as estimated by real-time RT-PCR. [50, 51]


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