Maryland ? The National Institutes of Health quietly blocked public access to databases of patient DNA profiles after learning of a study that found the genetic information may not be as anonymous as previously believed, the Los Angeles Times has learned.

NIH officials took the unusual step on Monday and removed two databases on the public Web site. The databases contained the genetic information of more than 60,000 cooperating patients. Scientists began posting the information publicly eight months ago for the purpose of furthering medical research.

Creators of the database had taken steps to mask the identities of individual patients, summarizing and aggregating the genetic information. However, the independent study released today reported that a new type of DNA analysis could confirm the identity of an individual in a pool of similarly masked data if that person’s genetic profile was already known.

Such a confirmation could reveal the patient’s participation in a study about a specific medical condition, experts said, and deny the patient their presumed confidentiality.