False-negative real-time polymerase chain reaction tests in COVID-19 patients: an epidemiological analysis of 302 patients.

OBJECTIVES: Patients who arrive at the emergency department (ED) with COVID-19, who test negative at the first real-time polymerase chain reaction (RT-PCR), represent a clinical challenge. This study aimed 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 and also 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 March 1 to May 15, 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 with positive cohort, but more comorbidities. Imaging helps to identify them. True positives had a higher risk of serious complications.

Immune response in relation to zinc status, sex and antioxidant defence in Italian elderly population: the ZENITH study.

OBJECTIVE: Evaluation of some immune markers in Italian elderly population in relation to zinc status, gender and antioxidant defence. DESIGN: Observational study. SETTING: Italian population. SUBJECTS: Apparently healthy, free-living subjects, 56 men and 52 women, aged 70-85 y, enrolled in Italy. METHODS: Lymphocytes were unstimulated or stimulated with the mitogen phytohemoagglutinin (PHA). The proliferative capacity was measured as incorporation of [3H]-thymidine and reported as stimulation index (SI). Cytokine secretion by lymphocytes was determined by ELISA. The antioxidant enzyme activities were measured using commercial kits. RESULTS: Dietary zinc intake, as well as zinc in serum, red blood cells and urine were on the normal range of values and did not show any difference between men and women. The proliferative response showed a high variability without significant differences between men and women. The amount of secreted pro- and anti-inflammatory cytokines was similar in men and women. No differences were found in the activity of antioxidant enzymes in lymphocytes, namely superoxide dismutase, glutathione peroxidase and catalase, between men and women. An association between SI and serum zinc level in men was found. SI resulted negatively correlated with interleukin (IL)-1beta (R2 = 0.036 and P = 0.012) and IL-10 (R2 = 0.34 and P = 0.040) only in men. IL-10 of PHA-stimulated lymphocytes was negatively correlated with red blood zinc in men (R2 = 0.41 and P = 0.008), while IL-10 of unstimulated and PHA-stimulated lymphocytes were negatively correlated with serum zinc in women (R2 = 0.38 and P = 0.020; R2 = 0.31 and P = 0.040, respectively). No correlation was observed between immune markers and antioxidant enzyme activities. CONCLUSIONS: Only weak differences on immune response between men and women were observed. However, zinc status appears to have more influence on the ability of lymphocytes to proliferate in men than in women.