The tools of diagnosis

Historically, diagnostic tools were developed as early at the 11th century. At that time, physicians diagnosed diabetes by tasting the urine of patients to detect sugar. Only in the 19th century was a chemical test developed to identify and quantify the presence of sugar in urine. In the 18th century, certain forms of heart disease were diagnosed by the physician simply placing an ear on the patient’s chest and listening to the heartbeat. Improperly closing valves, double beats, and other anomalies could be detected by the trained listener. In fact, in 1816, that particular physical technique was the genesis of the first modern diagnostic instrument. A French physician named Réné Laënnec was examining a woman patient in a setting in which modesty precluded any form of disrobing. Laënnec overcame this disadvantage by rolling up a piece of paper into a tube and placing one end on the patient’s chest, the other against his ear. To his surprise, the beating heart could be heard more clearly than with his ear alone, and thus was born the stethoscope. Two centuries later, most stethoscopes are still being used much as they were envisioned by Laënnec. But improvements are being made; witness the fact that in 1999, the U.S. Food and Drug Administration approved the medical use of a fully electronic stethoscope, capable of amplifying sounds up to 14 times higher than the standard stethoscope.

For many diseases, the diagnostic standard has moved well beyond the inspection (visually, aurally, or with the other senses) of the “macro” components of the body, inside and out, to one of molecular specificity. As the true causes of disease are discovered, the diagnostics endeavor has taken the idea of disease identification and cause to new depths. Mark Lesney’s piece, “Cancer: From detection through therapy”, details the powers of our greatly increased understanding of cancer-related proteins for opening up a new level of patient care. Not only can molecular profiling, via techniques such as immunohistochemistry, the polymerase chain reaction, and DNA microarrays, provide more definitive cancer detection, but they also have the potential to assess risk, determine patient prognosis, and predict drug resistance on an individual basis. “Diagnosing newborns”, by Randall Willis, focuses on the capacity of one particular technique, mass spectrometry, for diagnosing metabolic disorders in neonates and unearthing new biomarkers for such conditions.

There is no question that evaluating disease and determining the best course of treatment are, to a certain degree, a physician’s art. The taking of a medical history, combined with the trained eyes, ears, and hands of the modern doctor, is just as important today as it was in the 11th century. But the tools now becoming available that use genomic and proteomic data will one day be just as important as the drugs they produce.