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<p>This retrospective analysis examined the consistency of the results of routine preliminary police drug tests using saliva/oral fluid (OF-VT) or urine (urine VT) with those of the final, legally relevant blood sample analyses in the context of traffic controls. A&#xa0;total of 3570 completed traffic cases from the period between 1 August 2023 and mid-November 2025 were examined.</p><p>In almost half of the cases in which a&#xa0;preliminary test was performed, at least one of the parameters tested was inconsistent with the result of the subsequent blood sample: using the new legal THC limit (§&#xa0;24a&#xa0;StVG, Road Traffic Act) of 3.5 ng/ml in serum, there was at least one deviation in approximately 47% of cases with OF-VT and in approximately 48% of cases with urine VT compared to the findings of the corresponding blood sample; however, the discrepancy rates were already high based on the previous THC limit of 1.0 ng/ml (OF-VT: 39%, urine VT: 33%); therefore, the increased legal limit cannot be seen as a&#xa0;significant factor for the observed deviations.</p><p>The main causes of the high deviation rates are more likely to be attributed to problems inherent in preliminary testing, such as the mandatory matrix change, the time difference between the pre-test and blood collection and the low specificity of immunochemical methods. In addition, it was found that user and documentation errors also have a&#xa0;relevant influence on the apparent accuracy of the onsite screening tests.</p><p>A&#xa0;comparison of the two pre-test strategies revealed a&#xa0;relatively balanced profile of advantages and disadvantages: The urine VT is superior to the OF-VT in terms of false positive (FP) amphetamine findings (5% fewer) and the rate of false negative (FN) results for “hard” drugs but in contrast has almost 5% more FP results for THC (evaluated according to the new limit of 3.5 ng/ml). The risk of documentation or user errors was more apparent with OF-VT than with urine VT.</p><p>The results underscore that police preliminary testing can only serve as a&#xa0;supplement to qualified drug detection, not as a&#xa0;substitute.</p>

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Abgleich der Ergebnisse polizeilicher Routinevortests mit Blutanalysen: eine retrospektive Auswertung von Verkehrsfällen aus der Rechtsmedizin Essen

  • 期刊论文

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  • 发表日期：

    2026年4月27日

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  • Uta Küpper,
  • Benno Hartung

摘要

This retrospective analysis examined the consistency of the results of routine preliminary police drug tests using saliva/oral fluid (OF-VT) or urine (urine VT) with those of the final, legally relevant blood sample analyses in the context of traffic controls. A total of 3570 completed traffic cases from the period between 1 August 2023 and mid-November 2025 were examined.

In almost half of the cases in which a preliminary test was performed, at least one of the parameters tested was inconsistent with the result of the subsequent blood sample: using the new legal THC limit (§ 24a StVG, Road Traffic Act) of 3.5 ng/ml in serum, there was at least one deviation in approximately 47% of cases with OF-VT and in approximately 48% of cases with urine VT compared to the findings of the corresponding blood sample; however, the discrepancy rates were already high based on the previous THC limit of 1.0 ng/ml (OF-VT: 39%, urine VT: 33%); therefore, the increased legal limit cannot be seen as a significant factor for the observed deviations.

The main causes of the high deviation rates are more likely to be attributed to problems inherent in preliminary testing, such as the mandatory matrix change, the time difference between the pre-test and blood collection and the low specificity of immunochemical methods. In addition, it was found that user and documentation errors also have a relevant influence on the apparent accuracy of the onsite screening tests.

A comparison of the two pre-test strategies revealed a relatively balanced profile of advantages and disadvantages: The urine VT is superior to the OF-VT in terms of false positive (FP) amphetamine findings (5% fewer) and the rate of false negative (FN) results for “hard” drugs but in contrast has almost 5% more FP results for THC (evaluated according to the new limit of 3.5 ng/ml). The risk of documentation or user errors was more apparent with OF-VT than with urine VT.

The results underscore that police preliminary testing can only serve as a supplement to qualified drug detection, not as a substitute.