Exploratory evaluation of physiological markers within a treadmill prioritization framework in a predominantly male...

Exercise treadmill testing (TMT) is commonly used in occupational cardiovascular surveillance for safety-sensitive workers, but age-based screening may generate high volumes of asymptomatic examinations with relatively low event prevalence. This retrospective cross-sectional study evaluated whether routinely collected physiological indicators could support exploratory stratification of positive TMT responses within a treadmill prioritization (TP) framework. Occupational surveillance records were analyzed among rotational shift workers in the Indonesian oil and gas industry between January 2024 and December 2025. Universal TMT was performed in 3,631 workers (3,544 male, 87 female), with 40 positive TMT responses. Associations were evaluated using multivariable Firth logistic regression, and a reduced exploratory model including hemoglobin and estimated glomerular filtration rate (eGFR) was internally validated using bootstrapping. Higher hemoglobin was independently associated with lower odds of positive TMT response (adjusted OR 0.73; 95% CI 0.58-0.94). The reduced framework demonstrated moderate discrimination (optimism-corrected AUC 0.72) and visual calibration agreement. Within the derivation cohort, 409 workers (11.3%) were classified as low-risk, with no observed positive TMT responses. These findings suggest physiological reserve markers may provide exploratory stratification information alongside conventional risk indicators. However, the TP framework remains hypothesis-generating and should not modify TMT intervals or reduce testing before external validation.