In order to market the latest "fad drug" -- those that supposedly lower cholesterol rates -- pharmaceutical companies are quick to point out that medical studies proved their effectiveness.

Yet, according to an article in the Archives of Internal Medicine, a member of the Journal of the American Medical Association (JAMA) family of journals, few of those studies actually looked at the effect of the drug therapy on average people.

Researchers compared the cholesterol levels of patients in four large drug trials with those of patients enrolled in a major heart study (The Framington Heart Study) to determine whether the results of those trials could be generalized over the general population.

Both total cholesterol and high-density lipoprotein cholesterol (HDL-C, the "good" cholesterol) levels were compared.

The researchers found that 40% of the men and 80% of the women in the Framingham study had cholesterol profiles that were excluded from the large trials.

In general, individuals with desirable total cholesterol levels and lower HDL-C levels and those with average total cholesterol levels and average-to-higher HDL-C levels have never been included in these trials.

The researchers found that among subjects who developed coronary heart disease during the Framingham study follow-up, 25.1% of men and 66.2% of women would not have been eligible for any of the cholesterol-lowering therapy trials and most of these "ineligible" subjects had elevated triglyceride levels.

The research was headed by Donald M. Lloyd-Jones, M.D., from the National Institutes of Health, Bethesda, Md.

The problem with such a discrepancy is that the drugs or other medical therapy tested during the trials are very often prescribed to types of people who have not been tested.

"The applicability of primary prevention trials to patient groups who were not included in the study cohort is an important concern for clinicians and policy makers," the study concluded.