Quantitative measurement of ketone bodies in urine using reflectometry

Background: Recently, automated urine test strip readers became available that can report quantitative data. We explored the possibility of measuring all ketone bodies (acetone, acetoacetate, 3-hydroxybutyrate) in urine with these test strips. Monitoring urinary ketone concentrations could offer the advantages of measuring higher values (due to the low renal thresholds) and being less sensitive to fluctuations. Methods: We evaluated URISYS 2400 (Roche) quantitative reflectance data for the ketone reflectance field and compared it with biochemical data from urine samples. Using an easy sample pre-treatment with 3-hydroxybutyrate dehydrogenase, we were able to assay 3-hydroxybutyrate as well, which normally does not react on urine test strips. Results: Within- and between-run reproducibility of the reflectance signal for high- and low-concentration urine pools was 11.0-3.6% and 11.0-5.8% for acetoacetate, 8.2-9.2% and 10.4-16.1% for acetone, and 5.1-3.0% and 5.6-3.5% for 3-hydroxybutyrate, respectively. The lower limit of detection for acetoacetate was 0.13 mmol/L (CV=3.6%). Fair agreement was obtained between test strip data for ketones and colorimetrically determined acetoacetate values (r=0.90). Conclusions: In urine test strip analysis, quantitative ketone reflectance data allow a simple and fast analysis, offering affordable screening for the detection of ketone body production in diabetes, especially in emergency settings.