A trial protocol has inclusion criteria that every candidate must meet and exclusion criteria that veto a candidate anyway. This example screens four patients and produces both a status and a human-readable reason for each, the audit trail a trial coordinator needs.
Run it in the playground · Source
The protocol admits adults with type 2 diabetes whose HbA1c (a three-month average of blood sugar) lies between 7.0% and 10.5%. It excludes anyone whose eGFR (a measure of kidney function) is below 45 mL/min, and anyone who is pregnant.
Who is eligible, who fails screening, and for which reason?
age(p001, 54).
age(p002, 67).
age(p003, 31).
age(p004, 45).
lab(p001, hba1c_pct, 8.4).
lab(p002, hba1c_pct, 7.9).
lab(p003, hba1c_pct, 9.1).
lab(p004, hba1c_pct, 6.4).
lab(p001, egfr_ml_min, 83.0).
lab(p002, egfr_ml_min, 38.0).
lab(p003, egfr_ml_min, 91.0).
lab(p004, egfr_ml_min, 72.0).
condition(p003, pregnant).
All four have type 2 diabetes. Each lab value is a separate fact with its unit in the name, so the rules never guess what a number means.
inclusion_hba1c(Patient) :-
lab(Patient, hba1c_pct, Hba1c),
(Hba1c >= 7.0),
(Hba1c =< 10.5).
exclusion_renal(Patient) :-
lab(Patient, egfr_ml_min, Egfr),
(Egfr < 45.0).
screen_eligible(Patient) :-
inclusion_adult(Patient),
inclusion_diagnosis(Patient),
inclusion_hba1c(Patient),
\+ exclusion_renal(Patient),
\+ exclusion_pregnancy(Patient).
Each criterion is a named predicate, so it shows up by name in every proof. Eligibility requires all inclusions and the absence of a proven exclusion.
eyeprolog examples/clinical-trial-screening.pl
type(p001, trial_candidate).
status(p001, eligible).
status(p002, screen_fail).
status(p003, screen_fail).
status(p004, screen_fail).
reason(p001, "meets inclusion criteria and no listed exclusion").
reason(p002, "eGFR below renal safety threshold").
reason(p003, "pregnancy exclusion applies").
reason(p004, "HbA1c is outside protocol range").
Only p001 qualifies. Each of the other three fails for a different reason, and the reason facts say which.
eyeprolog --proof examples/clinical-trial-screening.pl
step(screen_eligible(p001),
rule(27),
['Patient' = p001],
[inclusion_adult(p001),
inclusion_diagnosis(p001),
inclusion_hba1c(p001),
\+ exclusion_renal(p001),
\+ exclusion_pregnancy(p001)]).
step(exclusion_renal(p002),
rule(25),
['Patient' = p002, 'Egfr' = 38.0],
[lab(p002, egfr_ml_min, 38.0), 38.0 < 45.0]).
p001 is eligible because all three inclusions hold and neither exclusion can be proved. p002 fails because its eGFR of 38.0 is below 45.0, and the proof points at the exact lab fact.
condition('C1', resolution, ok, 25).
condition('C6', boundary_consistency, ok, 3).
obligation(absent, theory_scoped, \+ exclusion_renal(p001)).
obligation(absent, theory_scoped, \+ exclusion_pregnancy(p001)).
obligation(absent, theory_scoped, \+ inclusion_hba1c(p004)).
verdict(checked_with_obligations).
The rule steps replay exactly. Three conclusions rest on something not being provable: that p001 has no renal or pregnancy exclusion, and that p004’s HbA1c is not in range. The checker cannot prove an absence in general, so it lists these as obligations. Condition C6 tested all three against the program’s facts and found nothing that contradicts them.
Learn more in The Art of EyeProlog, Chapter 7 and Chapter 25.