Optimizing genetic testing strategy for suspected attenuated adenomatous polyposis: effective solutions in public...

APC and MUTYH genes are key in hereditary attenuated adenomatous polyposis syndromes. Guidelines recommend genetic testing based on polyp count, often overlooking age despite its impact on polyp prevalence.

To enhance genetic testing strategies for suspected attenuated adenomatous polyposis by combining polyp count and age in a probability calculator.

Retrospective study of adult patients referred to NGS genetic testing for suspected attenuated adenomatous polyposis (accumulated history of < 100 adenomas) (discovery cohort, N = 138). Data included age, adenoma count, and test results. A multivariable logistic regression model was developed to associate positive genetic test results with age and adenoma count. The model was externally validated with 259 patients from two tertiary hospitals in our region (validation cohort, N = 259).

In the discovery cohort, 13 (9.4%) patients had pathogenic mutations, being younger (OR:0.91, 95%CI 0.86-0.96) and having more adenomas (OR:1.08, 95%CI 1.04-1.13) compared to negative cases. The logistic regression model combining age and polyp count demonstrated an AUC of 0.92. Using a cutoff probability of 3.5%, the model achieved 100% sensitivity and 58% specificity in identifying positive cases. In the external validation, the model accurately predicted 14 out of 16 positive cases (88%). The remaining two positive cases were a patient with an AXIN2 mutation in heterozygosis, and a patient with a NTHL1 mutation in homozygosis. Performance evaluation of both hospitals yielded AUC values of 0.77 and 0.90.

Older individuals with fewer polyps are less likely have hereditary syndromes. Including age in genetic testing criteria can enhance patient selection and cost-effectiveness.