Probing indiscretions: contamination of cardiac troponin reagent by very high patient samples causes false-positive results.

BACKGROUND

Cardiac troponin (cTn) has become the standard biomarker for the diagnosis of acute coronary syndromes. False-positive cTnI results have previously been reported on the Beckman Coulter analysers, which were shown to be random, not reproducible and occurred more commonly than expected. Our investigation ensued after a patient sample with an inordinately elevated cTnI was analysed, followed by a series of false-positive results being reported. The implications of falsely elevated cTnI results on patient care could be considerable.

METHODS

Multiple experiments with patient sample pools with concentrations below the 99th percentile to extremely high (0.025, 15, 175 and 884 μg/L) were conducted in varying sequences of high and low samples on the Beckman Coulter Access2, UniCel DxI600 and UniCel DxI800 analysers.

RESULTS

Our results demonstrate a significant increase in cTnI concentrations in the negative pool after analysis of high pool samples in various sequences. This increase is sufficient to cause elevations above the 99th percentile cut-off and false-positive cTnI results. These findings were reproducible on all three analysers.

CONCLUSIONS

Our study is highly suggestive of carryover and cTnI reagent pack contamination by the pipettors on the Access2, DxI600 and DxI800 analysers when patient samples with extremely high cTnI concentrations are analysed, leading to potential false-positive cTnI results on subsequent samples.