Evaluation of Imprecision for Cardiac Troponin Assays at Low-Range Concentrations

Abstract

has recommended that an increased cardiac troponin should be defined as a measurement above the 99th percentile value of the reference group. A total imprecision (CV) at the decision limit of <10% is recommended. However, peer-reviewed data on assay imprecision are lacking. The purpose of this study was to construct the clinically relevant imprecision profiles for each of the commercially available cardiac troponin assays. Pools of human sera containing cardiac troponin concentrations around the MI decision limit were assessed to identify the lowest concentration associated with a 10% CV. Methods: Eight serum pools targeting different concentrations of cardiac troponin (I and T) were prepared and stored at ؊70°C until usage. The cardiac troponin measurement protocol consisted of two replicates per specimen per run, and one run per day for 20 days, using two

Multicenter evaluation of analytical performance of the Liaison® troponin I assay

“…The LiaisonR cTnI assay revealed excellent performance if compared with data published for other commercial systems [15] and was quite close to meet the 10% CV at URL, demonstrating a 10%/99th ratio of 1.6. Our results corroborate those from a recent collaborative study in which the imprecision experiments directly performed by the assay manufacturer gave a 10% CV value of 0.065 Ag/l and a ratio of 2.2 [15]. Conversely, our findings from the imprecision studies are different from those published in a study showing a 10% CV at 0.027 Ag/l [19].…”

“…This value exceeds the 99th percentile URL (0.036 Ag/l), the theoretically defined AMI cut-off in the Joint European Society of Cardiology/American College of Cardiology document [3]. As recently shown in a comprehensive study [15], there are currently no commercial assays that can achieve the 10% CV recommendation at 99th percentile URL, so that, in the context of clinical practice, the use of a predetermined cTnI concentration that meets the 10% imprecision goal as an AMI cut-off has been suggested [16,17]. The use of the actual 10% CV concentration instead of 99th percentile URL as a decision cut-off could slightly decrease the clinical sensitivity of the biochemical criterion used for the AMI diagnosis but should permit the physician to avoid the occasional increase in serum cTnI in the absence of myocardial damage [18].…”

“…One using commercial controls showed good imprecision even for the low control, which was close to the 99th percentile URL. The other approach was to define the imprecision profile using the protocol recommended by IFCC to obtain a realistic indication of the variation of cTnI measurements especially at low-range concentrations [7,15]. For this latter study, pools of human sera were used.…”

“…The use of the actual 10% CV concentration instead of 99th percentile URL as a decision cut-off could slightly decrease the clinical sensitivity of the biochemical criterion used for the AMI diagnosis but should permit the physician to avoid the occasional increase in serum cTnI in the absence of myocardial damage [18]. The LiaisonR cTnI assay revealed excellent performance if compared with data published for other commercial systems [15] and was quite close to meet the 10% CV at URL, demonstrating a 10%/99th ratio of 1.6. Our results corroborate those from a recent collaborative study in which the imprecision experiments directly performed by the assay manufacturer gave a 10% CV value of 0.065 Ag/l and a ratio of 2.2 [15].…”

The 99th percentile of reference population for cTnI and cTnT assay: methodology, pathophysiology and clinical implications

“…Quality specifications for troponin assay require the presence of measurable cTnI and cTnT, also in the blood of healthy subjects [4][5][6]. However, measurement of the 99th URL of cTnI and cTnT levels is a challenging analytical issue due to low biomarker concentrations present in healthy subjects [7][8][9].…”