Point-of-care neutrophil CD64 as a rule in diagnostic test for bacterial infections in the emergency department.

INTRODUCTION: Bacterial infections are frequently seen in the emergency department (ED), but can be difficult to distinguish from viral infections and some non-infectious diseases. Common biomarkers such as c-reactive protein (CRP) and white blood cell (WBC) counts fail to aid in the differential diagnosis. Neutrophil CD64 (nCD64), an IgG receptor, is suggested to be more specific for bacterial infections. This study investigated if nCD64 can distinguish bacterial infections from other infectious and non-infectious diseases in the ED. METHODS: All COVID-19 suspected patients who visited the ED and for which a definitive diagnosis was made, were included. Blood was analyzed using an automated flow cytometer within 2 h after presentation. Patients were divided into a bacterial, viral, and non-infectious disease group. We determined the diagnostic value of nCD64 and compared this to those of CRP and WBC counts. RESULTS: Of the 291 patients presented at the ED, 182 patients were included with a definitive diagnosis (bacterial infection n = 78; viral infection n = 64; non-infectious disease n = 40). ROC-curves were plotted, with AUCs of 0.71 [95%CI: 0.64-0.79], 0.77 [0.69-0.84] and 0.64 [0.55-0.73] for nCD64, WBC counts and CRP, respectively. In the bacterial group, nCD64 MFI was significantly higher compared to the other groups (p < 0.01). A cut-off of 9.4 AU MFI for nCD64 corresponded with a positive predictive value of 1.00 (sensitivity of 0.27, a specificity of 1.00, and an NPV of 0.64). Furthermore, a diagnostic algorithm was constructed which can serve as an example of what a future biomarker prediction model could look like. CONCLUSION: For patients in the ED presenting with a suspected infection, nCD64 measured with automatic flow cytometry, has a high specificity and positive predictive value for diagnosing a bacterial infection. However, a low nCD64 cannot rule out a bacterial infection. For future purposes, nCD64 should be combined with additional tests to form an algorithm that adequately diagnoses infectious diseases.

Thrombotic events in COVID-19 are associated with a lower use of prophylactic anticoagulation before hospitalizationand followed by decreases in platelet reactivity

Background : Coronavirus disease of 2019 (COVID-19) is associated with a prothrombotic state and high incidence of thrombotic events (TE). Platelet hyperreactivity has been reported in COVID-19 patients and might contribute to TE development. Aims : To study platelet reactivity in hospitalized COVID-19 patients and to determine a possible association with the clinical outcomes thrombosis and all-cause mortality. Methods : 79 hospitalized COVID-19 patients were enrolled in this retrospective cohort study and provided blood samples in which platelet reactivity in response to stimulation with ADP and TRAP-6 was determined using flow cytometry. Clinical outcomes included thrombotic events, and all-cause mortality. Results : The incidence of TE in this study was 28% and all-cause mortality 16%. Patients that developed a TE were younger than patients that did not (median age of 55 versus 70 years;adjusted odds ratio (AOR), 0.96 per 1 year of age [95% CI, 0.92-1.00];P = 0.042). Furthermore, patients using preexisting thromboprophylaxis were less likely to develop a TE than patients that were not (18% versus 54%;adjusted odds ratio, 0.18 [95% CI, 0.04-0.82];P = 0.026). Conversely, having asthma strongly increased the risk on TE development (adjusted odds ratio, 6.4 [95% CI, 1.17-35.4];P = 0.032). No significant differences in baseline P-selectin expression or platelet reactivity were observed between the COVID-19 positive patients ( n = 79) and COVID-19 negative hospitalized control patients ( n = 24), nor between COVID-19 survivors or non-survivors. However, patients showed decreased platelet reactivity in response TRAP-6 following TE development compared to patients without TE. Conclusions : We observed an association between the use of preexisting thromboprophylaxis and a decreased risk of TE during COVID-19. This suggests that these therapies are beneficial for coping with COVID-19 associated hypercoagulability. This highlights the importance of patient therapy adherence. We observed lowered platelet reactivity after the development of TE, which might be attributed to platelet desensitization during thromboinflammation.