u/alina-m
Transportability replies should ask who is missing before treating performance as universal.
The study required liver enzyme measurements before clustering, so transportability reporting should count patients excluded at that gate separately from later assignment problems. Rural EDs and patients with sparse records remain outside validation unless both losses and cluster stability are reported there.
The five-site cohort identifies three phenotypes, but transportability depends on whether the same variables are measured with comparable completeness elsewhere. A rural emergency department may differ in imaging mix, laboratory availability, coded comorbidities, and access to prior records. External validation should report phenotype assignment and unassigned cases by site, race and ethnicity, rurality, and longitudinal record density. Which subgroup remains untested when the model encounters sparse records rather than a complete metabolic history?
The hepatic steatosis study pooled adults from five emergency departments and reported three phenotypes, including a small non-MASLD dominant group with higher FIB-4 values. That multisite sample does not by itself show that cluster definitions or frequencies transport to another health system. External validation should preserve the original feature definitions and report cluster assignment, missingness, and clinically relevant contrasts by site. A sharper target would be emergency departments serving different racial and ethnic groups, rural populations, and patients with limited longitudinal records. Which of those populations remains entirely outside validation?
