Gap between evidence and physicians' knowledge and practice regarding hypertension and its drug treatment: a survey in a Chinese city

Background Evidence-based medicine has come into its second decade. How prepared clinicians are in practicing it in particular in developing countries remains unclear. Thus we conducted this survey of physicians in urban hospitals in China to determine the size of the gap between research evidence and physicians' knowledge and practice regarding antihypertensive drugs for primary prevention of cardiovascular diseases in China. Methods A cross sectional survey by a face-to-face interview was conducted in 20 tertiary general hospitals in China in 2005. A total of 444 physicians (mostly cardiologists) in internal medicine who had treated at least one hypertensive patient in the past 12 months were invited for the interview on their perception of the cardiovascular risk of hypertension, the magnitude of the benefit of antihypertensive drugs, knowledge on the overall risk approach, first-line drugs used, the risk above which drug treatment is recommended, and knowledge on evidence-based medicine. Results A total of 444 of the 468 eligible physicians were successfully interviewed with a response rate of 94.9%. They estimated that a hypertensive man with an actual 5-year cardiovascular risk of 8.4% would have a 5-year cardiovascular risk of 40% (95% CI: 38% to 42%) if not treated, and have an absolute risk reduction and relative risk reduction from drug treatment by 20% (95% CI: 18% to 22%) and 39% (95% CI: 37% to 42%) respectively, as compared to 3.3% and 33% respectively shown in research evidence. On average, the physicians would recommend drug treatment at a number needed to treat (NNT) of 368 or smaller, as compared to the actual NNT of 50 for drug treatment in an average hypertensive Chinese. Fifty-five percent (95% CI: 50% to 59%) of them had never intently used the national hypertension guidelines. The majority still prescribed drugs primarily based on blood pressure alone by ignoring other risk factors or the overall risk and 78% (95 % CI: 76% to 83%) used new expensive drugs such as calcium channel blockers and angiotensin converting enzyme (ACE) inhibitors as first-line treatment. Only 13% (95% CI: 9% to 18%) could correctly interpret the NNT. Forty-three percent (95% CI: 39% to 48%) did not know the randomized controlled trial was scientifically the most rigorous among other study designs for evaluating the effectiveness of anti-hypertensive drugs. Ninety-two percent (95% CI: 90% to 94%) did not know they could start by searching systematic reviews when looking for evidence on the effectiveness of anti-hypertensive drugs as opposed to trials. Ninety-six percent (95% CI: 94% to 98%) did not know the Cochrane Library was an important source of systematic reviews. Conclusions The surveyed physicians significantly over-estimated the cardiovascular risk of hypertension and the benefit of drug treatment, and had insufficient knowledge on the overall risk approach. They recommended drug treatment at a cardiovascular risk which was even much lower than the cutoff suggested for western populations, which would make many more people eligible for drug treatment. They also tended to prescribe new expensive drugs although the older cheaper ones may be more appropriate in many patients. They showed inappropriate knowledge on the basics of evidence-based medicine.