From the Research
First catch urine refers to the initial portion of urine collected during urination, typically the first 10-30 milliliters, and is particularly valuable for detecting sexually transmitted infections (STIs) like chlamydia and gonorrhea. However, the most recent and highest quality study 1 suggests that there is no consistent evidence that asking women to provide midstream samples with or without cleansing is better than other methods, including first-void urine. The study found that there was no difference in contamination for MSU specimens collected with or without cleansing and between random void urine collection and MSCC. Key points to consider when collecting a first catch urine sample include:
- The sample should be collected after the patient has not urinated for at least 1-2 hours
- The initial stream should be captured directly into a sterile container without stopping the flow
- The sample should be capped immediately and processed within 24 hours, or refrigerated if testing will be delayed It's also important to note that the main contaminant in first-void urine samples was Enterococci spp., which contributed to the majority of false positives, as found in the study 2. In terms of diagnostic accuracy, the study 1 found that there was no difference in contamination rates between different urine sampling methods, including first-void urine, MSU, and random voiding samples. Overall, the most recent and highest quality evidence suggests that the choice of urine sampling method may not have a significant impact on diagnostic accuracy, and first catch urine may be a suitable option for detecting STIs.