American Medical Technologist (AMT) Practice Exam

In urine collection, what does a "midstream" technique help prevent?

1. Sampling too early in the voiding process

2. Contamination by skin flora

3. Inaccurate urine volume measurement

4. Evaporation of the specimen

The correct answer is: Contamination by skin flora

The midstream urine collection technique is specifically designed to minimize contamination of the urine sample by external factors, particularly skin flora and microorganisms present in the urethra. By asking the patient to initiate the stream of urine and then collect the sample after a short interval, the technique allows for the first portion of urine to wash away any potential contaminants that might be present in the urethra or on the skin around the urinary opening. This method is crucial for obtaining a clean and representative urine sample, especially in scenarios where the sample will be tested for bacteria or other pathogens. By reducing the likelihood of contamination, the accuracy of the subsequent laboratory tests is enhanced, leading to more reliable clinical decisions. While the other answer choices highlight important aspects of urine collection, they do not pertain to the primary purpose of the midstream technique as effectively. The focus on avoiding contamination by skin flora is the main reason for utilizing this method in clinical practice.