Zodpey Sanjay P, Shrikhande Sunanda N
Clinical Epidemiology Unit, Government Medical College, Nagpur, Maharashtra, India.
Indian J Public Health. 2007 Oct-Dec;51(4):205-10.
To study association between the geographic location (latitude) of studies evaluating protective effect of BCG vaccine and it's efficacy / effectiveness against tuberculosis.
A comprehensive literature search was carried out to identify relevant studies. Data extraction from these studies included place of study (geographic latitude), study design and reported point estimate of protective effect of BCG vaccine against tuberculosis. Information on latitude was obtained from Oxford School Atlas for World Geography. A spearman rank correlation coefficient was estimated to study the association between the latitude of studies and protective effect of BCG vaccine.
The Spearman's rank correlation coefficient was significant for all studies grouped together & trials and marginally non-significant for other observational studies. However it was not statistically significant for case-control studies and cohort studies. Overall rho (for 80 studies) between latitude and protective effect of BCG was calculated to be 0.3853 (p = 0.0004). The results thus demonstrated that, in general BCG appeared to provide greater protection at higher latitudes. Thus a correlation coefficient of 0.3853 between latitude and protective effect would indicate that (0.3853)(2) or 15% of the variance in protective effect was accounted for by latitude.
The study recognized an association between geographic locations of studies and reported protective effects of BCG vaccine against tuberculosis.
研究评估卡介苗（BCG）疫苗保护效果的研究的地理位置（纬度）与其预防结核病的效力/效果之间的关联。
进行全面的文献检索以识别相关研究。从这些研究中提取的数据包括研究地点（地理纬度）、研究设计以及卡介苗疫苗预防结核病的保护效果的报告点估计值。纬度信息来自《牛津世界地理学校地图集》。估计斯皮尔曼等级相关系数以研究研究纬度与卡介苗疫苗保护效果之间的关联。
对于所有汇总在一起的研究以及试验，斯皮尔曼等级相关系数具有显著性，而对于其他观察性研究则略微不显著。然而，对于病例对照研究和队列研究，其在统计学上并不显著。计算得出卡介苗的纬度与保护效果之间的总体rho值（针对80项研究）为0.3853（p = 0.0004）。结果表明，总体而言，卡介苗在较高纬度地区似乎能提供更大的保护。因此，纬度与保护效果之间的相关系数为0.3853表明，保护效果差异的（0.3853）² 或15%可由纬度解释。
该研究确认了研究的地理位置与报告的卡介苗疫苗预防结核病的保护效果之间存在关联。
