IsAdult Patient Category feature

[halcwb]

IsAdult Patient Category Facet

Date: 2026-05-18
Status: Accepted

Context

The FTK dose-rule extraction pipeline (see
docs/data-extraction/doserule-extraction-flowchart.md)
must capture source rules phrased categorically as "adults" (Dutch
volwassenen, and ouderen/bejaarden for elderly) where the source gives
no numeric age range. The core-domain.md Patient Category model is
defined strictly in terms of numeric ranges (age, weight, BSA, gestational
age, post-menstrual age, gender), so there is no existing way to represent
"applies to adults, age asserted categorically."

Decision

Introduce IsAdult as a standalone, positive-only boolean facet of
Patient Category:

• "x" means the rule applies to adults, asserted categorically; absence
  asserts nothing (it is never a negative — never "not an adult").
• When IsAdult = "x", the rule's numeric MinAge/MaxAge are intentionally
  emptied: the categorical adult assertion replaces the numeric age range.
• Elderly (ouderen/bejaarden) is deliberately folded into Adult — dosing
  rarely differs and a separate elderly band is not warranted.
• It is fully system-resolved by the extraction pipeline (preliminary keyword
  at Pass 1, confirmed at Pass 3); it is not a human-edited field and not the
  first value of a general age-band axis.

Considered Options

• Numeric adult floor (MinAge ≈ 6570 days) — rejected: loses the
  distinction between "rule explicitly bounded at 18 yr" and "rule applies to
  the adult category"; pollutes the numeric range with a synthetic value.
• Categorical AgeCategory axis (Adult / Neonate / Child / Elderly) —
  rejected: over-generalises; only Adult needs the categorical escape hatch,
  the other bands remain well-served by numeric ranges.

Consequences

• Blocking precondition (safety). No IsAdult = "x" row may reach GenFORM
  ingest until (a) Patient Category in GenFORM .fs carries the facet and
  (b) patient-matching enforces "adult patients only" for such rules. Until
  both exist, an IsAdult = "x" row has empty age bounds and an unconsumed
  flag, so it would match every age — directly violating the
  core-domain.md safety-by-construction / completeness guarantees.
• Hard to reverse. IsAdult is hashed into the Pass-4 GrpId/Id, and
  the clearing guard irreversibly erases MinAge/MaxAge in extracted TSVs.
  Reversing the model means re-running extraction on affected generics.
• core-domain.md and the GenFORM Patient Category type must be updated to
  record this single, deliberate exception to the ranges-only model when the
  facet is implemented in domain code.