Subjects and data collection
This cross-sectional study was conducted in 2020 to evaluate the serum levels of vitamin D, calcium, and zinc on the severity of the disease in patients with COVID-19, after obtaining the necessary permits from Shoushtar University of Medical Sciences. After receiving the required permission to collect data, the researcher went to the hospital and performed sampling by explaining the research objectives, obtaining patient satisfaction, and obtaining informed consent from the subjects.
This study was conducted from May 13 to May 30, 2020, on 93 COVID-19 patients admitted to Khatam al-Anbia Hospital in Shoushtar in southwestern Iran. For SARS-CoV-2 nucleic acid detection, the real-time reverse-transcriptase-polymerase-reaction (RT-PCR) was performed on nasopharyngeal and oropharyngeal swabs.
The subjects were selected via a purposive sampling method among COVID-19 patients admitted to Shoushtar Khatam Al-Anbia Hospital. Blood samples were taken from the patients by a hospital nurse (a project colleague) and sent to a private laboratory for more investigation.
Inclusion criteria were as follows: 1. having an Iranian ethnicity and being a resident of Shoushtar city; 2. being infected with COVID-19 based on PCR test; 3. having the willingness to participate in the study; 4. being over 15 years old, and 5. being fasting during sampling.
Exclusion criteria were as follows: 1- living outside of Shoushtar city 2- having dissatisfaction to participate in the study; 3- taking Vitamin D, calcium, and zinc supplements during the last six months before the study; 4- taking corticosteroid drugs, cholesterol-lowering drugs such as cholesterol and barbiturates and phenytoin (which they can reduce the serum levels of vitamin D, calcium and zinc in the body); 5. having parathyroid disease, bone disease, chronic liver disease, kidney disease, and cancer; and 6. having been treated with vitamin D, calcium and zinc.
Laboratory and clinical results
In this study, we measured serum levels of vitamin D, calcium, and zinc. Serum vitamin D levels were measured by ELISA (Enzyme-Linked Immunosorbent Assay). Serum levels of vitamin D were divided into 30ng/ml-100 ng/ml as sufficient, 10 ng/ml -30 ng/ml as insufficient, and < 10 ng/ml as deficient. Calcium Arsenazo measured serum levels of calcium with a reference range of 8.6–10.3 mg/dl. Serum levels of zinc were measured by Atomic Absorption Spectrophotometry (AAS) with a reference range of 70–127 µg/dl.
In this study, information such as age, gender, place of residence, calcium, zinc, and vitamin D supplementation, history of underlying diseases (diabetes, hypertension, heart disease, lung disease, hyperlipidemia); symptoms and possible complications of the disease (cough, shortness of breath). Stenosis, fever, muscle weakness, pain, nausea, vomiting, headache, dizziness, abdominal pain, seizures, chest pain, palpitations, blurred vision, diarrhea, restlessness, aggression, decreased sense of smell, etc.). Laboratory results such as serum levels of vitamin D, calcium, zinc, blood urea nitrogen (BUN), creatinine (cr), sodium (Na), potassium (K), white blood cell (WBC), red blood cell (RBC), hemoglobin (HB), hematocrit (HEMA), platelet (PLT), lymphocyte (Lym), neutrophils (Neut), Arterial Blood Gas Test (PH, PO2, PCO2, HCO3), erythrocyte sedimentation rate (ESR), and blood sugar (BS) were recorded.
According to the research objectives, previous studies (55), and the parameter of respiratory problems in COVID-19 patients in the two normal serum calcium and low serum calcium groups, the subjects' proportions with respiratory problems in the two groups were P1 = 0.06 and P = 0.016. Also, given β = 0.9, α = 0.05, d = 0.08 and using the sample volume ratio formula, the case group was estimated to consist of 93 subjects.
Blood test results, demographics, and clinical information were entered into IBM SPSS Statistics 18.0 software. Quantitative variables are reported as mean (average), standard deviation (mid-quarter range), minimum and maximum, and qualitative variables are reported as number (percentage). The Kolmogorov-Smirnov test was employed to confirm the normality of quantitative variables, the Spearman rank-order correlation coefficient to examine the relationship between quantitative variables, the independent t-test to compare means, the Kruskal-Wallis test to compare the levels of variables, the Chi-squared test to compare qualitative variables in terms of number, and sequential regression to predict some factors affecting the severity of COVID-19. The significance level of the above tests is considered less than 0.05.