False negative RT-PCR tests in COVID-19 patients: an epidemiological analysis of 302 patients

Caramello, Valeria; Macciotta, Alessandra; De Salve, Alessandro Vincenzo; Mussa, Alessandro; De Leo, Anna Maria; Bar, Fabrizio; Panno, Donata; Nota, Fabio; Ling, Camilla Yu Gi; Solitro, Federica; Ricceri, Fulvio; Sacerdote, Carlotta; Boccuzzi, Adriana

Background Patients who arrive at the Emergency Department (ED) with Coronavirus disease (COVID-19), who test negative at the first Real Time-Polymerase Chain Reaction (RT-PCR), represent a clinical challenge. Objectives To evaluate if the clinical manifestation at presentation, the laboratory and imaging results, and the prognosis of COVID-19 differ in patients who tested negative at the first RT-PCR compared with those who tested positive. Furthermore, to evaluate if comorbid conditions patient-related or the period of arrival are associated with negative testing. Study design We retrospectively collected clinical data of patients who accessed the ED from 1st March to 15th May 2020. Methods We compared clinical variables, comorbid conditions and clinical outcomes in the two groups by univariate analysis and logistic regression. Results Patients who tested negative at the first RT-PCR showed a higher prevalence of cardiopathy, immunosuppression and diabetes, as well as a higher leukocyte and lower lymphocyte counts compared with patients who tested positive. A bilateral interstitial syndrome and a typical pattern at Computed Tomography scan were prevalent in the test-negative group. Test-negative patients were more likely to be admitted to the hospital but less likely to need admission in a high level of care ward. The false-negative rate increased from March to May. Conclusion False-negative RT-PCR COVID-19 patients present a similar spectrum of symptoms compared to positive cohort, but more comorbidities. Imaging helps to identify them. True positives had a higher risk of serious complications.