Muhammad Aamir, Abdus Sattar, Mirza Muhammad Dawood, Muhammad Dilawar, Aamir Ijaz, Masood Anwar.
Hyperhomocysteinemia as a risk factor for ischemic heart disease.
J Coll Physicians Surg Pak Jan ;14(9):518-21.
Objective: To determine association of hyperhomocysteinemia with myocardial infarction and conventional risk factors for ischemic heart disease. Design: A non-interventional comparative case control study. Place and Duration of Study: The study was conducted at the department of Chemical Pathology and Endocrinology, Armed Forces Institute of Pathology, Rawalpindi and Armed Forces Institute of Cardiology / National Institute of Heart Diseases, Rawalpindi from January 2001 to June 2001. Patients and Methods: A total of 100 hospitalized patients having myocardial infarction (MI) were randomly selected comprising 85 males and 15 females. The average age of the patients was 53 ±4.5 years. A similar number of age and gender-matched healthy controls were also selected. The demographic details, history and clinical examination of both patients and controls were recorded and their blood was collected in fasting state for estimation of serum total cholesterol, plasma glucose and serum total homocysteine. Results: Serum total homocysteine level in controls was significantly lower (10.8 ± 4.1 mmol/L) as compared to patients (18.0 ± 5.9 mmol/L) (p < 0.0001). Smoking showed statistically significant association with hyperhomocysteinemic patients (p = 0.04). Conclusion: Ischemic heart disease was associated with moderate hyperhomocysteinemia in our patients and it was also associated with smoking.
I have reviewed the full-text article from the CPSP Web site. When the hyperhomocysteinemia has been established by so many previously well-documented study as one of the risk factors for CAD, what new aspect of this correlation has been evaluated in the current study? I don't want to go into the details of the metabolic mechanisms involved in the causation of hyperhomocysteinemia in the CAD patients (this area has been poorly disucussed in the said paper). I have reviewd the table 1 of and found that the statiscal analyses are quite incorrent. Let me consider the chi-squar test results for hypercysteinemia. In table 1, among the control subjects 3 had hypercysteinemia while 97 had normal homocystein level (below the cut-off value). Among 100 patients, 53 had elevated levels of homocystein (so hyperhomocysteinemic) while the remaining 47 subjects had normal homocystein levels. Whe I analyzed these values the chi-square test value is 62 while in table 1 of the article it is 38.6 see it at http://www.cpsp.edu.pk/jcpsp/Sep2004/518.asp My results for the said data values are as follows (to determine the risk of hypercysteinemia for CAD ... very sorry that the said paper remained confied chi-squar test to analyze its data):
Results of analysis done by me are
Exposure rate among diseased cases:0.53 or 53%
Exposure among healthy cases or controls: 0.03 or 3%
Incidence or absolute risk in the exposed group:0.946
Incidence or absolute risk in the non-exposed group: 0.326
Absolute risk in exposed + non-exposed groups: 0.5
Attributable risk (AR): 0.62
Attributable risk percent (AR%): 65.5%
Relative risk ratio (RR): 2.9
Odd that a diseased subject is exposed: 1.128
Odds that a conytrol (healthy) subject is exposed: 0.031
Odds ratio (OR) or cross-product ratio: 36.46
Chi-square test: 62
I don't know who among the evaluators for JCPS's articles approved articles with incorrect statistical analysis. Any statistician can easily reanalyze the data and will certainly approve my analyzed statical results.
Honesty group ... Fight against
Posted by: honesty on Sep 2004
Although I am confused by hinesty's calculation, especially by the use of relative risk in a case-control study, I do agree that the value of chi square is 62 (it reflects very poorly on the journal's standards, but it does not change conclusion).
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