Use of appropriate statistical tools in biomedical research: Current trend & status

Background & objectives: Due to lack of appropriate statistical knowledge, published research articles contain various errors related to the design, analysis and interpretation of results in the area of biomedical research. If research contains statistical error, however, costly, it may be of no use and the purpose of the investigation gets defeated. Many biomedical research articles published in different peer reviewed journals may retain several statistical errors and flaws in them. This study aimed to examine the trend and status of application of statistics in biomedical research articles. Study design, sample size estimation and statistical measures are crucial components of a study. These points were evaluated in published original research articles to understand the use or misuse of statistical tools. Methods: Three hundred original research articles from the latest issues of selected 37 journals were reviewed. These journals were from the five internationally recognized publication groups (CLINICAL KEY, BMJ Group, WILEY, CAMBRIDGE and OXFORD) accessible through the online library of SGPGI, Lucknow, India. Results: Among articles assessed under present investigation, 85.3 per cent (n=256) were observational, and 14.7 per cent (n=44) were interventional studies. In 93 per cent (n=279) of research articles, sample size estimation was not reproducible. The simple random sampling was encountered rarely in biomedical studies even though none of the articles was adjusted by design effect and, only five articles had used randomized test. The testing of assumption of normality was mentioned in only four studies before applying parametric tests. Interpretation & conclusions: In order to present biomedical research results with reliable and precise estimates based on data, the role of engaging statistical experts need to be appreciated. Journals must have standard rules for reporting study design, sample size and data analysis tools. Careful attention is needed while applying any statistical procedure as, it will not only help readers to trust in the published articles, but also rely on the inferences the published articles draw.

A tertiary care hospital-based study of conventional risk factors including lipid profile in proven coronary artery disease.

BACKGROUND: The prevalence and mortality rates of coronary artery disease have been known to be higher in the Indian than the Western population. Most data on lipid levels in Indians have been obtained from studies on migrant Asian Indians. There are insufficient data on lipid profile and other conventional risk factors in Indian patients living within India. METHODS AND RESULTS: The study included 2656 consecutive patients who underwent coronary angiography between March 1998 and February 2002. Of these, 2399 subjects had angiographically proven coronary artery disease (group 1) while 257 had normal coronary arteries (group 2). Lipid values were measured in the fasting state on the morning the coronary angiography was done. Patients receiving lipid-lowering agents, those having renal, hepatic or thyroid disorders, patients presenting within 8 weeks after acute myocardial infarction, and patients who were taking noncardiac drugs that affect the lipid profile were excluded from the study. Other conventional risk factors were also recorded. In subjects with coronary artery disease and normal coronary arteries, the levels of mean total cholesterol recorded were 178.5+/-42.1 mg/dl v. 154.1+/-40.2 mg/dl (p<0.001), high-density lipoprotein cholesterol 30.6+/-9 mg/dl v. 27.3+/-6.8 mg/dl (p<0.001), low-density lipoprotein cholesterol 109.8+/-35.4 mg/dl v 93.6+/-33.9 mg/dl (p<0.001), and triglyceride 190.7+/-95.4 mg/dl v. 157.6+/-73.5 mg/dl (p<0.001), respectively. In subgroup analysis by age, the younger coronary artery disease group (< or = 40 years) had significantly higher total and low-density lipoprotein cholesterol levels than the older group (> 40 years), viz. 194.6+/-51.4 mg/dl v. 176.3+/-40.2 mg/dl (p<0.001), and 118.3+/-39.6 mg/dl v. 108.7+/-36.1 mg/dl (p=0.001). Triglyceride levels were not significantly different [211.7+/-105.1 mg/dl v. 187.8+/-93.6 mg/dl (p=ns)], being equally high in both subgroups and, although high-density lipoprotein cholesterol levels were different, this difference was minimal, being equally low in both [32.7+/-9.5 mg/dl v. 30.3+/-9.0 mg/dl (p=ns)]. In the subgroup analysis of those with coronary artery disease, diabetics had significantly lower total cholesterol [174+/-41.1 mg/dl v. 180.4+/-42.4 mg/dl (p<0.001)] and low-density lipoprotein cholesterol levels [105.8+/-34 mg/dl v. 111.5+/-35.8 mg/dl (p<0.001)] than non-diabetics, whereas triglyceride and high-density lipoprotein cholesterol levels were not significantly different, triglycerides being equally high in both [186.2+/-95.5 mg/dl v. 192.5+/-95.2 mg/dl (p=ns)], and high-density lipoprotein equally low in both [30.9+/-9.3 mg/dl v. 30.5+/-9 mg/dl (p=ns)]. The commonest associated conventional risk factor in diabetics was hypertension and, in the younger age group (< or = 40 years), it was smoking and a positive family history of premature coronary artery disease. CONCLUSIONS: We conclude that in north Indians, coronary artery disease occurs at much lower levels of total cholesterol and low-density lipoprotein cholesterol than other populations, and high triglyceride and low high-density lipoprotein levels are more of a universal phenomenon in this population. Younger patients have a more atherogenic lipid profile than the older subgroup with coronary artery disease, and smoking and a family history of premature coronary artery disease are the most common associated risk factors. Total cholesterol levels seem to play a lesser role in the occurrence of coronary artery disease in diabetics, the presence of which is in itself overwhelming for the occurrence of coronary artery disease.

Drug sensitivity assay for leukaemic cells by flow cytometry.

BACKGROUND & OBJECTIVES: Drug sensitivity assays are useful in oncology practice for evaluating the sensitivity of malignant cells to anti-cancer drugs. The usefulness of such assays for the prediction of clinical response to therapy has also been demonstrated. The existing methods used for this purpose are time consuming and labour intensive. Here we report a simplified flow cytometry based assay for evaluating the in vitro drug sensitivity of leukaemic cells. METHODS: The chemo-sensitivity of three human leukaemic cell lines (a lymphoblastoid cell line, Jurkat; an erythroleukaemic cell line, K 562 and a myelomonocytic cell line HL-60) was investigated by flow cytometry. Flow cytometry was used to determine LD50 (50% inhibitory concentration) for prednisolone on Jurkat and daunorubicin on HL 60 and K 562 cell lines respectively. Per cent cell death could directly be assessed on a flow cytometer by measuring the fluorescence after staining with propidium iodide (PI). For comparison MTT assay was also performed using prednisolone on Jurkat and daunorubicin on HL-60. RESULTS: Cytotoxic effect of drugs was found to be dose dependent. Mean LD50 of prednisolone for Jurkat cells by flow cytometry was 0.805 +/- 0.058 mg/ml and by MTT assay 0.866 +/- 0.115 mg/ml. Mean LD50 of daunorubicin for HL-60 was 1.96 +/- 0.05 micrograms/ml by flow cytometry and 1.90 +/- 0.282 micrograms/ml by MTT assay. The mean LD50 of daunorubicin to K 562 was 0.49 +/- 0.049 mg/ml by the flow cytometry method. The inter-assay variation for the LD50 by flow cytometry based assay was found to be 6, 14 and 10 per cent for Jurkat, HL-60 and K 562 respectively. INTERPRETATION & CONCLUSION: We report a flow cytometry based drug-sensitivity assay for leukaemic cells, which uses a single dye staining and is rapid, technically simple and reproducible. The results compare well with the more commonly used MTT assay, which is labour intensive and time consuming. The limitation of our method is that it can only be used for studying cells in suspension and is therefore not suitable for adherent cell lines.