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Background: COVID-19 pathophysiology and the predictive factors involved are not fully understood, but lymphocytes dysregulation appears to play a role. This paper aims to evaluate lymphocyte subsets in the pathophysiology of COVID-19 and as predictive factors for severe disease. Patient and methods: A prospective cohort study of patients with SARS-CoV-2 bilateral pneumonia recruited at hospital admission. Demographics, medical history, and data regarding SARS-CoV-2 infection were recorded. Patients systematically underwent complete laboratory tests, including parameters related to COVID-19 as well as lymphocyte subsets study at the time of admission. Severe disease criteria were established at admission, and patients were classified on remote follow-up according to disease evolution. Linear regression models were used to assess associations with disease evolution, and Receiver Operating Characteristic (ROC) and the corresponding Area Under the Curve (AUC) were used to evaluate predictive values. Results: Patients with critical COVID-19 showed a decrease in CD3+CD4+ T cells count compared to non-critical (278 (485 IQR) vs. 545 (322 IQR)), a decrease in median CD4+/CD8+ ratio (1.7, (1.7 IQR) vs. 3.1 (2.4 IQR)), and a decrease in median CD4+MFI (21,820 (4491 IQR) vs. 26,259 (3256 IQR)), which persisted after adjustment. CD3+CD8+ T cells count had a high correlation with time to hospital discharge (PC = −0.700 (−0.931, −0.066)). ROC curves for predictive value showed lymphocyte subsets achieving the best performances, specifically CD3+CD4+ T cells (AUC = 0.756), CD4+/CD8+ ratio (AUC = 0.767), and CD4+MFI (AUC = 0.848). Conclusions: A predictive value and treatment considerations for lymphocyte subsets are suggested, especially for CD3CD4+ T cells. Lymphocyte subsets determination at hospital admission is recommended. [ABSTRACT FROM AUTHOR]

The prognostic value of the CD4+ T cell count is not clearly established for HIV-1 infected patients with an advanced immunosuppression. The aim of this study was to assess the relationship between CD4+ T cell counts and survival in patients with less than 50 CD4+ T cells per mm3 (/mm3). We examined an historical cohort of 97 patients with 2 consecutive CD4+ T cells determinations < 50/mm3 within 3 months, followed at a university hospital of the University of Montreal. The proportion of men was 93% with 74% being homo/bisexual. The means of the 2 CD4+ T cell counts/mm3 were 25 and 25.1 respectively. Median survival after the first CD4+ T cell count < 50 CD4+ T cells/mm3 was 15.2 months. Using the proportional hazard model, the median survival of patients with 2 consecutive CD4+ T cell counts < or = 20/mm3 was 9.3 months compared to 19.2 for those with 20-50 CD4+ T cells/mm3 (P < 0.0001). It seems then, that the CD4+ T cell count is a helpful prognostic marker, even in very immunosuppressed patients. Its prognostic value is more accurate if the measurement is replaced within 1-3 months because of high variability at this level of immunosuppression. [ABSTRACT FROM AUTHOR]