Which test requires the collection of both blood and urine at specific intervals?

The correct answer is glucose tolerance testing, which requires the collection of both blood and urine at specific intervals to assess the body's ability to metabolize glucose. This test is typically used to diagnose conditions such as diabetes mellitus or gestational diabetes.

During glucose tolerance testing, a patient ingests a specified amount of glucose, and subsequent blood samples are taken at set intervals to measure how effectively glucose is cleared from the bloodstream. Additionally, urine samples are collected during this period to monitor glucose and other metabolic byproducts. The combination of blood and urine tests provides a comprehensive view of the body's glucose handling over time, making it an essential diagnostic tool.

Other tests listed, such as blood cultures, lipid panels, and complete blood counts, do not involve urine collection or specific timed intervals for sample collection. Blood cultures are focused solely on blood samples to identify infections, lipid panels measure blood lipids at a single point in time, and complete blood counts provide a snapshot of various blood components without the need for urine samples. Thus, glucose tolerance testing stands out as the test that specifically integrates both blood and urine measurements over designated intervals.