FS2 evaluates the diagnostic accuracy and implementation feasibility of an AI-assisted blind-sweep obstetric ultrasound (SPAQ E-con AI), operated by trained non-specialist health workers, for antenatal screening in rural Democratic Republic of the Congo. Primary outcomes are gestational age mean absolute error (Trimester 2 and Trimester 3) with 95% confidence intervals and AI confidence calibration. The reference standard is manual measurement by a reference reader (early ultrasound first; manual BPD if unavailable; last menstrual period is not used). Target enrollment is approximately 1,430 (IRB-approved ceiling 3,000), with early termination permitted upon achievement of pre-specified analysis-plan thresholds. The study is a multi-center prospective Hybrid Type 1 Effectiveness-Implementation design and includes a pre-specified adaptive model-update (Batch 2 cut) plan following FDA PCCP and STARD-AI guidance.
Study Type
OBSERVATIONAL
Enrollment
3,000
Smartphone-based 9-sweep obstetric ultrasound with AI estimation of gestational age, fetal presentation, and placenta location, operated by trained non-specialist health workers after 30-60 minutes of training.
DPS Kwango
Kenge, Kwango, Democratic Republic of the Congo
RECRUITINGGestational age mean absolute error (MAE), Trimester 2 (14-27 weeks)
MAE in days vs reference standard, with 95% CI; target MAE ≤7 days and upper 95% CI ≤10 days
Time frame: Through study completion, up to 12 months
Gestational age mean absolute error (MAE), Trimester 3 (28-36 weeks)
MAE in days vs reference standard, with 95% CI; target MAE ≤10 days and upper 95% CI ≤14 days
Time frame: Through study completion, up to 12 months
AI confidence calibration - Expected Calibration Error (ECE)
Expected Calibration Error from the reliability diagram of AI confidence versus reference-standard agreement; target \<=0.05
Time frame: At Batch 1 closure, up to 8 weeks
AI confidence calibration - Brier score
Brier score of AI confidence versus reference-standard agreement; target \<=0.20
Time frame: At Batch 1 closure, up to 8 weeks
Trimester 1 gestational age MAE (CRL and GS models)
Integrated Cohort A T1 + Cohort B-2, N=30; CRL model MAE ≤5 days or GS model MAE ≤7 days
Time frame: Through study completion, up to 12 months
Placenta praevia and fetal malpresentation sensitivity and specificity
Observed sensitivity/specificity with 95% CI (Clopper-Pearson) on enriched validation subset (Cohort B-1, target N=20-25); reported as observed values
Time frame: Through study completion, up to 12 months
Inter-rater reliability of gestational age - Intraclass Correlation Coefficient (ICC)
ICC(2,1) between two independent readers for gestational age in days
Time frame: During the inter-rater assessment window, up to 1 week
Inter-rater reliability of placenta praevia classification - Cohen's kappa
Cohen's kappa for placenta praevia (yes/no) between two independent readers
Time frame: During the inter-rater assessment window, up to 1 week
Inter-rater reliability of fetal presentation classification - weighted kappa
Linear weighted kappa for fetal presentation category between two independent readers
Time frame: During the inter-rater assessment window, up to 1 week
Acceptability - Acceptability of Intervention Measure (AIM) score
Mean AIM score (4-item, 5-point Likert) among health workers
Time frame: Through study completion, up to 12 months
Feasibility - ultrasound throughput (scans per device per day)
Number of scans completed per device per day; target \>=15
Time frame: Through study completion, up to 12 months
Fidelity - protocol adherence rate (5-item checklist)
Percentage adherence on a 5-item fidelity checklist; target \>=80%
Time frame: Through study completion, up to 12 months
Penetration - proportion of eligible women screened
Percentage of eligible women in the catchment screened with AI ultrasound
Time frame: Through study completion, up to 12 months
Sustainability - intention to continue use
Percentage of staff reporting intention to continue use at the end-of-study interview
Time frame: At study completion, up to 12 months
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