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Z-score for benchmarking reader competence in a central ECG laboratory
Gopi Krishna Panicker1, Dilip R Karnad, Rajesh Joshi
1Quintiles ECG Services, Mumbai, India. gopi.panicker@quintiles.com
Summary
Z-scores effectively define reader competence for electrocardiogram (ECG) QT interval measurements in central laboratories. This method also helps identify specific measurement errors for targeted training.
Area of Science:
- Cardiology
- Medical Imaging Analysis
- Biostatistics
Background:
- Electrocardiograms (ECGs) from thorough QT studies require expert central laboratory analysis.
- Current standards for defining reader expertise in ECG interpretation are lacking.
- This study investigated the utility of Z-scores for establishing reader competence.
Purpose of the Study:
- To develop and validate a quantitative method for assessing reader competence in QT interval measurement.
- To establish objective criteria for defining acceptable performance in ECG reading.
- To identify patterns of measurement errors using Z-score analysis.
Main Methods:
- Calculated Z-scores for QT measurements from 200 ECGs read by 24 experts.
- Defined reader competence using the highest mean absolute Z-score as a cutoff.
- Assessed the performance of central laboratory readers using standardized ECGs.
Main Results:
- All experts achieved mean absolute Z-scores ≤ 1.5.
- One experienced reader and seven trainees initially had unacceptable Z-scores, but improved after retraining.
- Histogram analysis revealed distinct patterns of systematic bias (shorter/longer measurements) or inconsistent errors.
Conclusions:
- Mean absolute Z-score serves as a reliable metric for evaluating reader competence in QT interval measurement.
- Z-score analysis, particularly histogram examination, can precisely identify and categorize QT measurement inaccuracies.
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