From the Research
Not using first morning urine for a male GC/CT NAAT test may slightly reduce test sensitivity, but is generally acceptable if the patient has not urinated for at least 1-2 hours before sample collection. First morning urine is preferred because it contains the highest concentration of organisms after overnight accumulation in the urethra, potentially improving detection of infections, especially low-level ones. However, NAAT tests are highly sensitive regardless of collection time, with sensitivity rates above 90% for both gonorrhea and chlamydia, as seen in a study published in 2019 1. If a non-first morning sample must be used, patients should avoid urinating for at least 1-2 hours before collection and provide the first portion of the urine stream (first-catch). Excessive fluid intake before testing should be avoided as it may dilute the sample.
Key Considerations
- The sensitivity of NAAT tests for GC/CT in male urine samples is high, with a study from 2019 reporting a sensitivity of 98.4% for CT and 100% for NG 1.
- The use of non-first morning urine samples may slightly reduce test sensitivity, but this reduction is generally considered acceptable in clinical practice.
- Patients should be instructed to avoid urinating for at least 1-2 hours before sample collection and to provide the first portion of the urine stream (first-catch) to minimize the impact on test sensitivity.
Clinical Implications
- If there's high clinical suspicion but a negative non-first morning result, consider repeating the test with first morning urine or using additional collection sites like pharyngeal or rectal swabs depending on sexual practices.
- The convenience of non-first morning collection often outweighs the small potential decrease in sensitivity in most clinical settings, as noted in a study from 2017 2.
- NAAT tests have been shown to be effective in detecting GC/CT infections in various populations, including those screened at community-based organizations 3.