(Bloomberg) — Genetic tests for breast cancer risk often look for DNA flaws that haven’t been reliably linked to the disease, a new report found, casting doubt on diagnostics that examine dozens of genes to calculate a patient’s susceptibility.

Only 11 genes have potential mutations shown to raise the chance of getting breast cancer, according to the article published Wednesday in the New England Journal of Medicine. Some genes included in tests by Illumina Inc. and other companies haven’t been conclusively tied to breast cancer risk, the report said.

The cost of analyzing DNA -- the molecule containing the body’s code for making proteins, cells and tissues -- has dropped precipitously, and companies have added breadth to genetic tests for breast cancer risk. Yet more may not necessarily be better, according to an international team of researchers led by Douglas Easton, a cancer epidemiologist at the University of Cambridge in the U.K.