Commentary on the PASC Score for Long COVID: Comparing Clinical and Statistical Diagnostic Accuracy (Azola et al., JGIM)

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The authors argue that Azola et al’s Long COVID clinic cohort likely overrepresented patients with multiple symptoms, creating spectrum bias in sensitivity estimates.
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Requiring cases to have at least 1 neuropsychiatric symptom may have inflated sensitivity; 62% reported brain fog, worth 3 PASC score points.
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The specificity cohort of fully recovered individuals and healthy controls did not represent patients with overlapping symptoms from other causes, potentially inflating specificity.
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The authors note that case-control validation cannot establish positive or negative predictive values because it does not reflect disease prevalence in a population of interest.
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The authors conclude that the PASC score was not validated because sensitivity, specificity, and predictive value estimates were biased.

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