Positive anti-SARS-CoV-2 rapid serological test results among asymptomatic blood donors

The world is fighting with a COVID-19 pandemic, some of the uncertainties have been revealed. To figure out an estimation of asymptomatic patients and seropositive SARS-COV-2 blood donors in Iran, a national survey was conducted to find the prevalence of asymptomatic blood donors with positive SARS-COV-2 IgM/IgG test results at the end of May 2020.

From all 31 provinces, 1339 blood donors were included. At first, data was collected with an interview containing demographic data, risk factors and possible signs and symptoms held for each donor by a trained medical expert. Then, SARS-COV-2 serologic rapid tests were conducted. Subsequently, the test results were observed and recorded; all of their photos were checked by one single expert. We corrected the prevalence rates for sensitivity and weighted them by the last year rate of blood donation of each province.

The corrected prevalence rates of positive serological test results for sensitivity in provinces were between zero and 38.24%. The national prevalence was calculated 14.45% after weighting. Out of 161 positive donors, only 43 cases reported related signs or symptoms during the defined period of time, while 118 (73.29%) seropositive cases had not reported any related signs or symptoms. Some signs or symptoms were reported more frequent in the SARS-COV-2 serologic rapid test positives. The highest OR (10.19) was linked to ageusia.

This study has shown the prevalence of seropositive results to be around 14% in target population in which around ¾ had not reported any signs or symptoms.