Can saliva samples replace blood work?

• Position: Diagnostic Testing

Spitting into a cup or licking a diagnostic test strip someday could be an attractive alternative to having blood drawn at the doctor's office. Researchers have identified the largest number of proteins to date in human saliva, a preliminary finding that could pave the way for more tests based on saliva samples. Such tests show promise as a faster, cheaper, and potentially safer method than blood sampling.

"There is a growing interest in saliva as a diagnostic fluid, due to its relatively simple and minimally invasive collection," points out study leader Phillip A. Wilmarth of Oregon Health & Science University School of Dentristry, Portland. "The same proteins present in blood are also present in saliva from fluid leakage at the gum line. It is considerably easier, safer, and more economical to collect saliva than to draw blood, especially for children and elderly patients."

While saliva tests will not replace blood tests for all diagnostic applications, in the future they could prove to be a potentially life-saving alternative to detect diseases where early diagnosis is critical, such as certain cancers. Saliva collection also may be the only practical way to screen large numbers of patients in developing nations.

Diagnostic assays using saliva are a relatively new, but growing, technology. The Food and Drug...