What instructions should be given to a patient regarding a 24-hour urine collection?

The correct answer involves ensuring that the patient collects all urine produced over the full 24-hour period and storing the container appropriately, either on ice or in the refrigerator. This is crucial for the accuracy of the test because a 24-hour urine collection is designed to measure the total amount of a substance excreted in urine over an entire day. Collecting urine throughout the entire day, including overnight, is essential to obtaining a complete and representative sample. Storing the collection on ice or in the refrigerator helps to preserve the integrity of the sample and prevent degradation of the substances of interest, which can impact test results.

Other options suggest inadequate procedures. Limiting collection to just daytime hours would lead to missing urine produced overnight, which could skew results. Ignoring urine with a strong odor could result in omitting an important portion of the total output, while collecting only the first urination of the day would not fulfill the requirement for a complete 24-hour sample. Overall, following proper collection and storage methods is critical for the reliability of test results from a 24-hour urine collection.