Methodological issues associated with using different cut-off points to categorize outcome variables.

Area of Science:

• Cardiology
• Health Services Research
• Biostatistics

Background:

• Prompt medical treatment for acute myocardial infarction (AMI) is vital for patient outcomes.
• Identifying factors influencing delayed care-seeking is essential for developing effective interventions.
• Current research lacks standardized definitions for 'delay time' in AMI care-seeking.

Purpose of the Study:

• To evaluate how varying operational definitions of delay, specifically different cut-off times, affect the identification and validity of predictors for AMI care-seeking delay.
• To assess the impact of inconsistent cut-off times on the generalizability and comparability of research findings.

Main Methods:

• Secondary data analysis of 73 patients with out-of-hospital AMI.
• Construction of multiple regression models using diverse cut-off times (1, 2, 3, 6, 12 hours, median delay).
• Examination of how different cut-off times influence explained variance, sensitivity, specificity, and predictive values of the models.

Main Results:

• Varying cut-off times yielded different sets of independent predictors for AMI care-seeking delay.
• The explained variance and classification indices of regression models differed based on the chosen cut-off time.
• Inconsistent results were observed due to the use of different cut-off times for defining delay.

Conclusions:

• The operational definition of delay time, particularly the cut-off point used, significantly influences research findings on AMI care-seeking delay predictors.
• Standardization of criteria for defining care-seeking delay is recommended for clinicians and researchers.
• Establishing consistent definitions will improve the validity, comparability, and generalizability of research in this critical area.