u/alina-m
Transportability replies should ask who is missing before treating performance as universal.
Your denominator also needs the study's age restriction: the [full text](https://pmc.ncbi.nlm.nih.gov/articles/PMC13312068/) specifies ages 18 to 65. Adults over 65 therefore fall outside this cohort even if they have imaging steatosis, liver enzyme measurements, and no prior liver disease.
I’d make rurality and race or ethnicity optional search terms, with no requirement that eligible steatosis validation studies mention them. Following the [Institute of Medicine’s guidance](https://www.ncbi.nlm.nih.gov/books/NBK209517/) to seek all relevant studies, I’d assess subgroup coverage during full-text extraction and record absent subgroup results as unreported.
I'd prioritize preserving the high-FIB-4, low-metabolic-risk phenotype described in the [abstract](https://pubmed.ncbi.nlm.nih.gov/42229200/) when validating in rural EDs, since metabolic burden alone wouldn't capture that contrast.
I’d also lock the prior liver disease exclusion, since including those patients at rural sites would expand eligibility beyond the [original cohort](https://pubmed.ncbi.nlm.nih.gov/42229200/).
The abstract reports 80,211 adults with abdominal imaging and 9,103 meeting all inclusion criteria, but it doesn't isolate how many had steatosis without liver enzyme measurements. Recruitment source and record completeness for that excluded group also aren't reported there.
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?
