COVID-19: Persistent Symptoms After Mild Illness / When to Test Student Contacts? / Pulse Oximetry Limitations

By Amy Orciari Herman

Edited by David G. Fairchild, MD, MPH

Here are some of the latest findings on COVID-19:

Persistent symptoms after mild illness: One third of patients with mild COVID-19 may report ongoing symptoms 6 months later, according to a small study in JAMA Network Open. Roughly 180 adults completed health questionnaires at a median of 5.5 months (range, 1–10 months) after developing COVID-19; the large majority had been outpatients with mild illness. Some 33% of patients with mild illness and 31% of those who'd been hospitalized reported at least one persistent symptom — compared with 5% of a healthy control group. Fatigue and loss of smell/taste were most commonly reported (14% of all patients). Other symptoms included headache, trouble breathing, and muscle aches. Overall, 31% of patients reported worse health-related quality of life relative to baseline. The authors write, "Our research indicates that the health consequences of COVID-19 extend far beyond acute infection, even among those who experience mild illness."

When to test student contacts? Testing student contacts of confirmed COVID-19 cases 9 days after exposure — and allowing asymptomatic contacts with negative results to return to school — can safely rule out SARS-CoV-2 infection and limit the number of school days missed, researchers report in JAMA. Some 840 student contacts (elementary through high school) of 260 confirmed student cases in Florida were tested for SARS-CoV-2 between 9 and 14 days after exposure (the protocol called for testing on day 9). Roughly 5% had positive results — most on day 9 or 10, and most often high school students. Of contacts who tested negative and returned to school, just one subsequently had a positive result, on day 14, and the virus was genetically distinct from the virus to which the student had been exposed. Approximately 3650 fewer school days were missed with the 9-day testing protocol compared with a 14-day quarantine plus no testing strategy. The researchers note, "These findings should be considered when evaluating the December 2020 CDC recommendation for a 10-day quarantine without testing or a 7-day quarantine with testing."

Pulse oximetry limitations: The FDA is alerting healthcare providers that pulse oximeters have varying accuracy depending on a person's circulation; skin pigmentation, thickness, or temperature; smoking status; and use of nail polish. In particular, the agency cites a recent study, published in the New England Journal of Medicine, in which pulse oximetry failed to detect occult hypoxemia nearly three times as often in Black patients as in white patients. The FDA advises clinicians to use trends in pulse oximetry readings over time (rather than absolute cutoffs) to make patient care decisions, if possible. The agency also notes that readings should be used as an estimate of oxygen saturation; for instance, a reading of 90% generally means a patient's oxygen saturation is between 86% and 94%. In addition, clinicians should be aware that pulse oximeters are most accurate at readings of 90% and above — and least accurate below 80%.