Automated microscopy was validated as a specimen validity test for urine. Over 99% of 1127 outpatient urine specimens contained cells and other elements at an average of 25.5 per microscopic field. Five of 250 pain management specimens and 10 of 10 commercial synthetic products were deemed potentially nonphysiologic by microscopy.
ABSTRACT
Synthetic products are marketed for specimen substitution and can be difficult to identify because many contain creatinine, urea, and pH buffers designed to meet acceptance criteria of common specimen validity tests. Methods involving DNA analysis and liquid chromatography–mass spectrometry have been successful in detecting synthetic products, but of these require significant sample preparation, lengthy analyses, and/or complex technical analysis. The aims of this study were to characterize the properties of commonly available synthetic urine products in order to determine new methods of detection, or provide information that might help others determine methods to detect synthetic urine products. Physical evaluations, clinical urinalysis, mass spectrometry, and microscopic analysis were used to evaluate 10 synthetic urine products, and results were compared to authentic human specimens. Two of 10 synthetic products exhibited lasting bubbles or foam after shaking. None of the synthetic products contained cells or formed biological elements. In contrast, 99% of 1127 outpatient specimens and 98% of the 250 pain management specimens evaluated in this study contained biological elements. The automated microscopy analyzer used in this study exhibited 100% sensitivity, 98% specificity, required no specimen pretreatment, provided results in less than 2 min, and was interfaced to the laboratory information system for rapid and accurate reporting. Given that normal human urine contains over 1 million cells per liter, microscopic analysis may provide an effective method to differentiate synthetic products from authentic urine. The shake test followed by microscopic analysis should provide an efficient and effective combination to detect synthetic urine products.
