Accuracy-based proficiency testing for estradiol measurements

• Published in: Clinical biochemistry 2024-02, Vol.124, p.110700, Article 110700
• Main Authors: Tim Cao, Zhimin, Rej, Robert, Vesper, Hubert, Rex Astles, J.
• Format: Article
• Language: English
• Subjects: Accuracy; Estradiol; Proficiency testing; Standardization
• ISSN: 0009-9120; 1873-2933; 1873-2933
• DOI: 10.1016/j.clinbiochem.2023.110700

•Traditional proficiency testing (PT) cannot identify inaccurate estradiol methods.•Estradiol results from commutable PT samples were compared to CDC target values.•Biases were 34% (−17% to 175%) and 40% (−33% to 386%) for the two lowest samples.•Scores were affected by the acceptance limit criteria and use of peer-grouping.•Improvement in estradiol measurement is needed, particularly at low concentrations. Accuracy of estradiol measurements is important but conventional proficiency testing (PT) cannot assess accuracy when possibly non-commutable samples are used and method peer-group means are the targets. Accuracy-based assessment of estradiol measurements is needed. Five serum samples were prepared from single donors, frozen, and distributed overnight to 76 New York State Department of Health (NYSDOH)-certified laboratories. Participants analyzed samples for estradiol. The biases of group means were assessed against the Centers for Disease Control and Prevention (CDC)-defined targets, evaluated using the Hormone Standardization Program (HoSt) E2 performance criterion of ±12.5 %. Each laboratory’s performance was evaluated using total allowable error (acceptance limits) of target ±25 % or ±15 pg/mL (55 pmol/L) (whichever was greater, NYSDOH), target ±30 % (Clinical Laboratory Improvement Amendments [CLIA]), and target ±26 % (minimal limit based on biological variation [BV]). The biases (range) were 34 % (−17 % to 175 %), 40 % (−33 % to 386 %), 16 % (−45 % to 193 %), 5 % (−27 % to 117 %), and −4% (−31 % to 21 %), for samples at estradiol of 24.1, 28.4, 61.7, 94.1, and 127 pg/mL, or 89, 104, 227, 345, and 466 pmol/L, respectively. Large positive method/analytical systematic biases were revealed for 9 commonly used method/analytical systems in the United States at low estradiol concentrations. Of the 9 analytical systems, 0, 0, 3, 7 and 6 met the HoSt criterion for the samples with estradiol at the five respective concentrations. PT evaluation showed that 59 %, 69 % and 87 % of laboratories would receive a PT event passing (satisfactory) score when the CDC-defined target and a criterion of NYSDOH, CLIA or BV was used, respectively. However, >95 % laboratories would obtain PT passing score if method peer-group means were used as targets regardless of the criterion used. Improvement in accuracy of estradiol measurements is needed, particularly at low estradiol concentrations. Accuracy-based PT provides unambiguous information about the accuracy of methods/ana