What laboratory test should a nurse expect to be ordered for a client with suspected osteomyelitis?

In cases of suspected osteomyelitis, the erythrocyte sedimentation rate (ESR) is often elevated due to the inflammatory response associated with the infection in the bone. ESR is a nonspecific test that measures the rate at which red blood cells settle at the bottom of a test tube over a specified period. An increased ESR indicates the presence of inflammation, which can be due to infection, conditions like osteomyelitis, autoimmune diseases, and even some cancers.

The other tests listed do not specifically indicate the presence of infection or inflammation in the bone. Serum potassium levels are primarily assessed for electrolyte balance and cardiac function; serum creatinine levels are indicative of kidney function; and prothrombin time (PT) is used to evaluate coagulation status and bleeding risk. Therefore, among the options presented, ESR is the most relevant laboratory test for diagnosing osteomyelitis.