Amid concerns about rising rates of medical errors, a new study finds that close to half of hospital outpatients taking medications for chronic illnesses failed to receive recommended laboratory tests aimed at spotting dangerous side effects.

Researchers at the Lovelace Respiratory Research Institute, in Albuquerque, N.M., identified the problem after tracking nearly 100,000 patients prescribed medications for chronic illnesses over a period of three years. Between 44 to 47 percent of patients failed to receive one or more recommended tests, the investigators found.

Experts advise that patients taking certain medications on an ongoing basis receive annual or more frequent lab testing in order to prevent drug-related complications, the study authors noted. Previous research has suggested that as many as 60 percent of preventable drug complications are related to laboratory monitoring errors.

Although their study found that lapses are common in outpatient drug safety monitoring, the researchers said more research is needed in order to assess to what extent these gaps result in actual medical problems.

Patients who are prescribed medications for chronic illnesses need to ask their doctors about tests to monitor side effects, the researchers advised.