Is it necessary to confirm the results of drug screening with a 2d analytical method

: Systematic analyses of positives from urine drug screening with immunochemical techniques have shown the importance of the confirmation of results by a chromatographic procedure. 15 to 30% of false positives can be encountered for opiates. The confirmation technique should have better sensitivity (and specificity) in order to discard divergence from differences between detection limits. Potential false negatives or falsification of positives are discussed. Propositions for a coherent behavior in the Swiss situation are given.