During an obstetric diabetes clinic, many patients tested positive for blood and protein in the urine by means of routine urine dipsticks. All samples were retested, but it was not until the end of the clinic that we noticed that Multistix SG strips (Bayer) had been used in one of the two Clinitek 50 meters instead of the intended Multistix 8 SG strip. This had led to repeated false positive results for blood and protein in every patient, empirical antibiotic treatment in one patient with symptoms of urinary tract infection, multiple requests for midstream urine microscopy (one of which revealed asymptomatic candidiasis), and potentially false negative results in patients to whom this test is extremely important.
Multistix SG strips test for glucose, bilirubin, ketone, specific gravity, blood, pH, protein, and urobilinogen, whereas Multistix 8 SG strips test for glucose, ketone, specific gravity, blood, pH, protein, nitrite, and leucocytes (listed in order on strips). The eight-test strips and meter had recently replaced a 10-test strip and meter throughout the hospital as a cost saving measure. Staff training was provided. The new meter was calibrated to detect colour changes in the order in which they appear on the Multistix 8 SG strips, but both versions of the eight-test strips had been supplied in case the bilirubin and urobilinogen tests previously available on the 10-test strip were needed. The bottles of strips look virtually identical (figure), but the order of tests varies.
While technology may improve efficiency and safety, the right materials and technique are vital to avoid compromising patient care. In this case the patients were rechecked, the problem was reported to the relevant hospital departments immediately, and staff were retrained. We informed the Medical Devices Agency and supplier of the problem and suggested that the eight-test strip bottles should be redesigned to appear less similar. 