A recent article published on news-medical.net discussed a study that compared three manufacturers' instruments and reagent strips after exposing the test strips to room air. The study reported that exposing the contents in strip bottles to humidity in room air could compromise strip integrity, cause reagent degradation and ultimately lead to false results and incorrect diagnosis.
The reagent strip and analyzer combinations used for this study were - Clarity® UROCHECK strips read on the Urocheck 120 Analyzer (Diagnostic Test Group), MULTISTIX 10 SG strips read on the CLINITEK Status+ Analyzer (Siemens Healthcare Diagnostics), and CHEMSTRIP® 10 MD strips read on the Urisys 1100® Analyzer (Roche Diagnostics).
Two sets of reagent strips were prepared for each manufacturer. The first set of bottles were opened and left exposed for 40-plus days to room air and room humidity to simulate the exposure the reagent strips could receive when an operator does not correctly close the strip container. In the second set, the bottles were left sealed until the urine sample was tested. About 200 patient urine samples were tested across all three combinations of brands for analytes such as leukocytes, occult blood, protein, nitrate, ketone and more.
The key findings of the report are as follows:
- When tested on the CLINITEK Status+ Analyzer, over 95% of the stressed MULTISTIX 10 SG strips returned error flags which accurately indicated that the reagent strips had been affected and are therefore not suitable for use.
- MULTISTIX 10 SG strips are designed to return an error flag instead of an actual result as soon as the system detects that the strips have been potentially affected because of excess exposure to environmental humidity.
- The Roche and Diagnostic Test Group analyzers do not feature a humidity detection system. Although the test strips were being affected by excess humidity, these two instruments reported results for patient samples.
- The results reported by the Roche and Diagnostic Test Group analyzers could be erroneous because analyte results varied between unexposed (unstressed) and exposed (stressed) test strips even for the same patient sample. It was observed that the cover in the urine-strip bottles had been partly or fully removed most of the time.
The study concluded that integrated with Auto-Checks technology this CLINITEK Status+ Analyzer and MULTISTIX 10 SG strips combination enables automatic detection of reagent strips that could have been affected by too much humidity. Auto-Checks technology automatically detects test strip humidity overexposure, checks for common sample interferences and identifies the Siemens reagent strip type, thus eliminating manual data entry and saving time.
The analysis highlights the necessity for testing entities to strongly enforce the recommendations of individual manufacturers to keep strip containers capped when strips are not being taken off for further analysis. It would also be beneficial for labs to ensure compliance by employing a system that would inform the tester about any affected strip and thus not enable testing.