A simple blood test may soon permit doctors to identify people at high risk for frequent urinary tract infections. Known as UTIs, these infections are some of the most common bacterial diseases, second only to respiratory infections in frequency. Women are much more likely than men to be afflicted by such infections, reports the National Kidney Foundation, which estimates that 10 to 20 percent of women will experience a UTI at least once. Up to 80 percent of those women will get recurrent infections, the foundation said.

The new test, developed by researchers at the Memorial Sloan-Kettering Cancer Center in New York, could help identify those at risk of repeated infections. That, in turn, could help pinpoint people who would benefit from aggressive preventive treatment, such as taking antibiotics.

Studies suggest that the test can be accurate in children as young as age 2. The simple test involves drawing a small amount of blood. Researchers then type the blood for a test known as Lewis blood groups, much the same way that they can categorize blood along the A, B, O blood types.

A study of 98 women found that those who have two specific types of Lewis blood groupings are almost four times as likely as other women to develop frequent urinary tract infections, said Joel Sheinfeld, an assistant attending surgeon at Memorial Sloan-Kettering and a developer of the test.

Sheinfeld, who discussed the new test at a recent science writers' meeting sponsored by the National Kidney Foundation, said that a study in children also showed the association between these two Lewis blood groupings and an increased risk of infection. The Lewis test is available at hospitals and blood banks throughout the country, although few doctors are using the test to screen for those at risk of recurrent UTIs.

Exactly what causes susceptiblity to UTIs is not completely understood. Preliminary evidence suggests that in people with the two Lewis blood types, cells lining the urinary tract are more receptive to bacteria attaching to the cell wall, leading to an infection.