Calculating the sample size in scientific studies is one of the critical issues as regards the scientific contribution of the study. The sample size critically affects the hypothesis and the study design, and there is no straightforward way of calculating the effective sample size for reaching an accurate conclusion. Use of a statistically incorrect sample size may lead to inadequate results in both clinical and laboratory studies as well as resulting in time loss, cost, and ethical problems. This review holds two main aims. The first aim is to explain the importance of sample size and its relationship to effect size (ES) and statistical significance. The second aim is to assist researchers planning to perform sample size estimations by suggesting and elucidating available alternative software, guidelines and references that will serve different scientific purposes.

Background It is known that inflammatory responses play an important role in the pathophysiology of COVID‐19. Aims In this study, we aimed to examine the role of kynurenine (KYN) metabolism on the severity of COVID‐19 disease AQ5. Materials & Methods Seventy COVID‐19 patients of varying severity and 30 controls were included in the study. In addition to the classical laboratory parameters, KYN, tryptophan (TRP), kynurenic acid (KYNA), 3 hydroxykynurenine (3OHKYN), quinolinic acid (QA), and picolinic acid (PA) were measured with mass spectrometry. Results TRP, KYN, KYN:TRP ratio, KYNA, 3OHKYN, PA, and QA results were found to be significantly different in COVID‐19 patients (p < 0.001 for all). The KYN:TRP ratio and PA of severe COVID‐19 patients was statistically higher than that of mild‐moderate COVID‐19 patients (p < 0.001 for all). When results were examined, statistically significant correlations with KYN:TRP ratio, IL‐6, ferritin, and procalcitonin were only found in COVID‐19 patients. ROC analysis indicated that highest AUC values were obtained by KYN:TRP ratio and PA (0.751 vs 0.742). In determining the severity of COVID‐19 disease, the odd ratios (and confidence intervals) of KYN:TRP ratio and PA levels that were adjusted according to age, gender, and comorbidity were determined to be 1.44 (1.1–1.87, p = 0.008) and 1.06 (1.02–1.11, p = 0.006), respectively. Discussion & Conclusion According to the results of this study, KYN metabolites play a role in the pathophysiology of COVID‐19, especially KYN:TRP ratio and PA could be markers for identification of severe COVID‐19 cases.

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Chitotriosidase (CHIT) belongs to the family of glycosylhydrolases and is highly homologous to chitinases from lower organisms. The enzyme CHIT is of interest for clinical reasons, because it is selectively expressed in chronically activated tissue macrophages. In most ethnic groups, approximately 6% of all individuals are homozygous for CHIT deficiency. Pathological tissue macrophages in several disease conditions massively express CHIT. A shared feature of such cells in the different conditions is the accumulation of lipid material in the lysosomal apparatus. Serum CHIT activity is significantly increased in individuals suffering from atherosclerosis disease and is related to the severity of the atherosclerotic lesion, suggesting a possible role as atherosclerotic extent marker. Our objective is to determine the levels of serum CHIT activity in healthy elderly subjects. Healthy 90 (between 65-94 years old) elderly people and 69 (between 20-44 years old) young people were chosen. Serum CHIT enzymatic activity was determined with the flurometric enzyme activity assay using artificial 4-MU substrate. We found CHIT activity 270 +/- 21 (nmol/mL/h) (values are mean +/- SD) in elderly people and 136 +/- 17 in young people. There are statistical differences between elderly and young subjects.

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