The Clinician-reported Genetic testing Utility InDEx (C-GUIDE) for Prenatal Care: Initial evidence of content and construct validity.

Objective: To develop and assess the face and construct validity of the Clinician-reported Genetic testing Utility InDEX (C-GUIDE^TM) for genetic testing in prenatal care.

Methods: Following a literature review and consultation with clinical experts, a preliminary draft of C-GUIDE Prenatal was developed. Its face and content validity were then assessed by 19 prenatal genetics' providers using interviews and surveys. Feedback informed further revisions. To test construct validity, four geneticist raters completed C-GUIDE on a retrospective sample of cases that received prenatal genetic testing and completed a concurrent global assessment of utility of these cases using an anchor item. A generalized estimating equations model was used to adjust for rater correlation and measure the association between C-GUIDE scores, global item scores, and potential clinical variables.

Results: To develop C-GUIDE Prenatal, 7 items were removed, 10 items were modified, and 4 items were added. For 101 cases rated for validation, on average, a 1-point increase in the global item score was associated with an increase of 1.1 in the C-GUIDE score (p=0.04). Compared to uninformative results, informative positive and informative negative results were associated with a mean increase of 10.7 (SE=1.05) (p<0.001) and 5.6 (SE=1.85) (p<0.001), respectively. As indications for testing, known/familial variants were associated with a mean increase in the C-GUIDE score of 4.7 (SE=2.21) (p < 0.001) compared to ultrasound findings. C-GUIDE scores increased by a mean of 3.0 (SE=0.23) among cases for whom pregnancies were ongoing compared to those for whom they were not (p<0.01).

Conclusions: The significant positive associations between C-GUIDE total and the global item score and between C-GUIDE total, result type, indication for testing, and pregnancy status in the expected directions provide evidence of construct validity.