Q&A: IDSA issues updated diagnostic guidelines for COVID-19
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Key takeaways:
- In some cases, experts recommend against routine serologic testing.
- The only clinical situation with a strong recommendation for testing was in pediatric patients suspected of having multisystem inflammatory syndrome.
The role of serologic testing for SARS-CoV-2 has evolved during the pandemic, leading the Infectious Diseases Society of America to update its guidance.
After reviewing available literature on COVID-19 serological testing, a panel of experts gathered by IDSA determined that the high seroprevalence of antibodies against SARS-CoV-2 worldwide “limits the utility of detecting anti-SARS CoV-2 antibody.”
Because of this, some of the updated guidance recommends against serologic testing to diagnose COVID-19 in the first 2 weeks after symptom onset, against the use of serologic testing to provide evidence of COVID-19 in symptomatic patients with a high clinical suspicion and against routine serologic testing among patients with previous infection or vaccination.
Healio spoke with Mary K. Hayden, MD, James Lowenstine professor of internal medicine, professor of pathology, and director of the division of infectious diseases and of the division of clinical microbiology at Rush University Medical Center, for more information about the updated guidance.
Healio: What prompted these guidelines?
Hayden: These guidelines were a scheduled update to the IDSA COVID-19 diagnostic guidelines. The original guidelines were written during a dynamic period in the COVID-19 pandemic. The panel wanted to review the large amount of data that had been generated since publication of the first guideline, anticipating that the new knowledge would result in changes to our original recommendations.
Healio: What are the key recommendations?
Hayden: Given that the global seroprevalence of SARS-CoV-2 antibodies is close to 100%, testing for antibodies has very limited clinical value. The only clinical situation for which the panel gave a strong recommendation in favor of testing (based on very low certainty of evidence) was in pediatric patients suspected of having multisystem inflammatory syndrome. In this situation, the panel recommended both nucleic acid amplification testing, and SARS-CoV-2 IgG. The panel recognized, though, that the positive predictive value of SARS-CoV-2 IgG even in this situation was low; the negative predictive value was higher.
Healio: Can you summarize the data backing up these recommendations?
Hayden: The data were derived from a systematic review of the literature and are provided in supplementary materials. The strength of evidence that was available to answer questions ranged from very low to low to moderate, which reduced the confidence of our recommendations.
Healio: Are there plans to reassess/update the guidance in the future?
Hayden: The plan is to combine the three diagnostic guidelines (molecular, antigen and serology) into a single document in the future.
Healio: What’s the key takeaway?
Hayden: As stated earlier, the key takeaway is that the global seroprevalence of SARS-CoV-2 is so high — nearly 100% in most populations — that serologic testing is of very limited clinical value. This is similar to serologic testing for other respiratory viral pathogens. We don't typically use serology to diagnose infections due to viruses like influenza, rhinovirus, etc.
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