To the editor:
The screening for coronavirus disease 2019 (COVID-19) is challenging: many patients are asymptomatic, viral RNA detection in a nasopharyngeal swab is falsely negative in 30%, and a pulmonary computed tomography scan is useless in patients with no pulmonary involvement.1 , 2
In our hemodialysis center, following the Kidney Disease Improving Global Outcomes recommendations, ferritin levels are measured each month to detect iron deficiency.3 In April 2020, there were 22 COVID-19 cases that had occurred within the 270 patients undergoing hemodialysis at our hemodialysis center. We noticed that ferritin levels were very high in these patients (Figure 1 ). When monthly ferritin levels were measured in April, 1 of our female patients had an unusually high ferritin level of 3806 ng/ml compared with 531 ng/ml previously. A clinical examination showed no clinical symptoms of COVID-19, but she was tested by nasopharyngeal swab and was shown to be positive.
Figure 1.
Ferritin levels of coronavirus disease (COVID)–negative (n = 268) and COVID-positive (n = 22) patients receiving hemodialysis at our center prior to and at COVID diagnosis. (a) Comparison of ferritin levels during the first week of March 2020 (before the coronavirus disease 2019 [COVID-19] epidemic had occurred at our center) and at diagnosis of COVID-19 (Student t test). The first COVID-19 case in our center was diagnosed on March 18, 2020. (b) Rate of patients with ferritin levels greater than 800 ng/ml during the first week of March 2020 and at diagnosis of patients who tested negative and positive for COVID-19 (χ2 test).
We compared ferritin levels in patients undergoing hemodialysis who tested positive and negative for COVID-19 at our dialysis center in the month preceding viral infection and during infection and found a critical difference (Figure 1). In the patients who tested positive for COVID-19, the mean (±SD) ferritin levels in March (before viral infection) and at diagnosis were 584 ± 318 and 1446 ± 1261 ng/ml, respectively, which was a mean increase of 275%. Interestingly, ferritin levels were increased at diagnosis in the 5 asymptomatic patients as well as in the patients with symptoms (mean ± SD, 1209 ± 1292 and 1535 ± 1280 ng/ml, respectively). Ferritin levels remained stable or decreased very slowly during the whole period of sickness in almost all patients. The pathophysiological mechanisms underlying high ferritin levels have not been totally explained at this time, and some investigators have reported a cytokine storm syndrome or macrophage activation syndrome; however, in our cohort, ferritin levels were not correlated with C-reactive protein (data not shown).4 , 5
Screening for COVID-19 in hemodialysis centers is crucial so that infected patients can be isolated and to protect noninfected patients. Ferritin could be a helpful, available, and easy-to-use screening tool for the disease, although we believe that more research still is needed.
References
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