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There was an increase in mortality risk among U.S. male veterans hospitalized with COVID-19 coronavirus infection who received hydroxychloroquine (HCQ) compared to those with no HCQ exposure, researchers found in a retrospective analysis.

Risk of death was higher among patients treated with HCQ versus those who only received standard care, albeit with a wide confidence interval (adjusted HR 2.61, 95% CI 1.10-6.17, P=0.03), reported Jayakrishna Ambati, MD, of the University of Virginia School of Medicine in Charlottesville, and colleagues.

There was a non-significant difference in risk of mechanical ventilation with HCQ alone versus standard care, with a similar wide confidence interval (adjusted HR 1.43, 95% CI 0.53-3.79, P=0.48), the authors wrote in a .

Combining HCQ with azithromycin showed mixed results. Patients in that category showed a trend toward reduced risk of mechanical ventilation (adjusted HR 0.43, 95% CI 0.16-1.12), but also a weak trend toward higher mortality (adjusted HR 1.14, 95% 0.56-2.32), both with respect to the standard care group.

"This nationwide retrospective study of the largest integrated healthcare system in the United States provides the largest dataset yet reported of the outcomes of COVID-19 patients treated with hydroxychloroquine, with or without azithromycin, anywhere in the world," they wrote.

Hydroxychloroquine, an antimalarial also used in the treatment of various autoimmune diseases, has been authorized by the FDA for emergency use in the treatment of COVID-19 "when clinical trials are unavailable or infeasible."

NIH guidelines released on Tuesday said there was "insufficient clinical data" to using chloroquine or hydroxychloroquine for treatment of COVID-19, cautioning only that clinicians should monitor patients for adverse effects, especially prolonged QTc interval.

Study investigators examined data from 368 patients who were hospitalized with COVID-19 in U.S. Veterans Health Administration medical centers from March 9 to April 11. Median age was about 69 and roughly two-thirds of patients were black. Patients were categorized according to drug exposure: HCQ alone, HCQ with azithromycin, or no exposure in addition to "standard supportive management." Primary outcomes were death and need for mechanical ventilation, and statistics were propensity-score adjusted on the basis of more than 40 clinical characteristics.

Data from 385 patients were available, but only 17 were women, and that number was "too small to permit robust statistical analyses" for sex differences, Ambati and colleagues indicated. There were no significant differences in baseline characteristics. with median age of patients ranging from 68 to 70, and about 60% to 68% were black.

Overall, 97 patients were exposed to HCQ alone, 113 to HCQ plus azithromycin (AZ), and 158 received standard care without HCQ. Unadjusted rates of death among patients in the HCQ and HCQ+AZ groups were 27.8% and 22.1%, respectively, compared with 11.4% with standard care.

The authors noted that HCQ, with or without azithromycin, was more likely to be prescribed to patients with more severe disease -- meaning increased mortality may have been expected -- but this risk remained after adjustment for propensity to receive the drug.

Rates of ventilation were lowest in the HCQ+AZ group (6.9%) and slightly lower in the HCQ group (13.1%) versus standard care (14.1%).

"That there was no increased risk of ventilation in the hydroxychloroquine-only group suggests that mortality in this group might be attributable to drug effects on or dysfunction in non-respiratory vital organ systems," the authors wrote, noting HCQ use in patients has been associated with cardiac toxicity.

Study limitations included the non-randomized treatments, potential for residual confounding or selection bias, and that results are not necessarily generalizable to women or younger patients.

"These findings highlight the importance of awaiting the results of ongoing prospective, randomized, controlled studies before widespread adoption of these drugs," Ambati and colleagues concluded.

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