Overweight and obese women are more likely to receive a false-positive result on mammography screening than women of normal weight or underweight, according to an article in the May 24th issue of the Archives of Internal Medicine.

According to information in the article, obese postmenopausal women have an increased risk of breast cancer compared with postmenopausal women of normal weight. It has been hypothesized that women with larger breasts may be less able to feel breast lumps, making it likely that their breast cancer will be diagnosed at a more advanced stage. However, the influence of obesity on mammography screenings has not been well studied.

In the current study, Joann G. Elmore, MD, MPH, and her American colleagues investigated the relationship between obesity and accuracy of mammography, analyzing 100,622 mammograms done as cancer screens. Body mass index (BMI) was assessed and mammography screening accuracy was determined. Participants were categorized based on their index: underweight or normal weight, BMI less than 25; overweight, BMI 25 to 29; obesity class I, BMI 30 to 34; and obesity classes II to III, BMI of 35 or higher.

The researchers found that "Compared with underweight or normal weight women, overweight and obese women were more likely to be recalled for additional tests after adjusting for age and breast density."

Overweight women were 17 percent more likely to be recalled, women in the obese category I group were 27 percent more likely to be recalled, and women in the obese category II and III groups were 31 percent more likely to be recalled.

"A woman's weight may influence the accuracy of screening mammography in several important ways," wrote the authors. "Obese women had more than a 20 percent increased risk of having a false-positive mammogram result compared with underweight and normal weight women. We did not find statistically significant improvements in sensitivity in obese women to counter this increase in false-positive rates. Understanding the quality of mammography among obese women is important, especially since the American population is becoming more obese and obesity is a modifiable risk factor."