Impact of external female urinary catheter use on urine chemistry test results

Abstract

We aimed to evaluate how urine chemistry tests are impacted by collection using a female external urinary catheter employing wicking and suction, to assess this catheter's potential as an alternative to transurethral catheters for collecting urine samples from incontinent patients. We obtained 50 random 40mL refrigerated urine specimens from excess volume submitted to the Michigan Medicine Biochemical Laboratory. Specimens were split into a 10mL "control" sample simulating voided urine, and a 30mL paired "wicked" sample applied dropwise to and collected from a fresh PureWick system simulating collection from an incontinent patient. Each sample pair was tested for glucose, sodium, potassium, creatinine, urea, total protein, and derived ratios of sodium/creatinine, urea/creatinine, and protein/creatinine, then compared using Pearson correlation coefficients. Wicking materials were imaged via absorption contrast tomography on a laboratory X-ray microscope, to study the structure through which urine passes. Control and wicked urine samples had very similar results for all chemical tests evaluated: strong Pearson correlation coefficients ranging from 0.955 (potassium) to 0.997 (glucose). Microscopic assessment of the amorphous wicking materials demonstrated an average pore spacing of 95.38µm. Common urine chemistry tests were unaltered by collection using the PureWick female external catheter system. This external device can be used to collect urine for chemistry tests as an alternative to transurethral catheters.