Sex differences in electrolyte imbalances caused by SARS-CoV-2: a case-control study

Background: - Since SARS-CoV-2 spread, evidences regarding sex differences in progression and prognosis of COVID-19 have emerged. Besides this, studies on patients’ clinical characteristics have described electrolyte imbalances as one of the recurrent features of COVID-19. Methods - We performed a case-control study on all patients admitted to the emergency department (ED) from 1st March to 31st May 2020 who had undergone a blood gas analysis and a nasopharyngeal swab test for SARS-CoV-2 by rtPCR. We defined positive patients as cases and negatives as controls. The study was approved by the local ethics committee Area 3 Milan. Data were automatically extracted from the hospital laboratory SQL-based repository in anonymized form. We considered as outcomes potassium (K+), sodium (Na+), chlorine (Cl-) and calcium (Ca++) as continuous and as categorical variables, in their relation with age, sex and SARS-CoV-2 infection status. Results - We observed a higher prevalence of hypokalemia among patients positive for SARS-CoV-2 (13.7% vs 6% of negative subjects). Positive patients had a higher probability to be admitted to the ED with hypokalemia (OR 2.75, 95% CI 1.8-4.1 p<0.0001) and women were twice as likely to be affected than men (OR 2.43, 95% CI 1.67-3.54 p<0.001). Odds ratios for positive patients to manifest with an alteration in serum Na+ was (OR 1.6, 95% CI 1.17-2.35 p<0.001) and serum chlorine (OR 1.6, 95% CI 1.03-2.69 p<0.001). Notably, OR for positive patients to be hypocalcemic was 7.2 (95% IC 4.8-10.6 p<0.0001) with a low probability for women to be hypocalcemic (OR 0.63, 95% IC 0.4-0.8 p=0.005). Conclusions - SARS-CoV-2 infection is associated with a higher prevalence of hypokalemia, hypocalcemia, hypochloremia and sodium alterations. Hypokalemia is more frequent among women and hypocalcemia among men.