Why 'not listed' does not mean 'no anticholinergic activity'

A search result can be incomplete in several different ways

When a medication does not appear in a scale, the immediate finding is about the list: no matching verified entry has been located in the version being used. That is a narrower statement than “the medication has no anticholinergic activity.” Confusing the two turns an information gap into a biological conclusion.

The distinction matters for both readers and software. A blank comparison cell may look like a technical inconvenience, but filling it with zero changes the evidence. A trustworthy medication tool preserves the missing state and, when possible, explains why it exists. It does not require every source to say something about every medicine.

Some medicines were outside the source’s scope

An instrument may have been developed for a particular country, prescribing environment or population. Medications unavailable there may never have entered the candidate list. Some source methods also exclude routes or product types. The KABS development publication explicitly describes formulary-based selection and exclusion of topical agents.

An excluded product has not necessarily been evaluated and found inactive. It was outside the set considered for that source. The correct response is to retain the scope limitation and seek other relevant evidence if needed. Assigning zero would misrepresent an eligibility decision as an experimental result.

Publication date creates another boundary. A list cannot be assumed to classify every medication or formulation introduced afterward. An old document can remain useful as a historical source while being incomplete for a later medication list. Its age is a reason to identify the version clearly, not a reason to rewrite its missing entries.

A name may not identify the intended record

Medication names can differ because of spelling, salt, active moiety, combination products or route-qualified labels. A search that fails to find an exact string does not prove the medication is absent from the source. Conversely, a similar string does not prove that a record is the correct match.

UnifiedACB retains preferred names and original source labels in the public dataset. The preferred name helps organize retrieval; it does not erase the source wording. An unresolved identity question should be clarified before a score is attached. Guessing a match and guessing a zero are different errors with the same consequence: the evidence appears more certain than it is.

Public availability is another distinct issue

A project can know that a scale exists without redistributing its medication table. The UnifiedACB source registry records reuse and integration information separately from public observations. Some source metadata therefore appears even when its medication-level rows are not part of the public dataset.

That boundary should be described as a public-data limitation. It does not establish that the original source omitted the medicine or assigned no activity. Readers can consult the linked source where appropriate, while the public interface avoids filling a restricted or unavailable row with another source’s value.

A documented omission shows why inference is risky

The preserved KABS notes include doxepin and chlorpromazine omissions from a medication-list supplement despite category header counts that suggest a mismatch. Those documented anomalies are visible rather than repaired by inventing a row. A category total does not supply the missing medication label, score and locator.

Quinupramine provides a related example. It is searchable as a provenance-only concept, with a note about main-text evidence, while no missing medication-list row is inferred. The record can communicate that the literature contains relevant information without pretending that every document contains the same entry.

These examples are not instructions to ignore other evidence. They show how to add context while preserving what each document actually says. A verified finding from another source can be displayed alongside a gap; it cannot retroactively become a row in the source that lacks it.

What to say when a value is unavailable

The most useful explanation identifies the missing item and the boundary: “No verified public observation is available from this source version.” If the reason is known, add it. If it is not known, leave that uncertainty explicit. Avoid wording that implies the medicine has been cleared of anticholinergic activity.

For the same reason, absence from UnifiedACB’s selected geriatric overlay is not a safety finding. The AGS strong-anticholinergic reference list is not a comprehensive list of all medications with relevant properties. A supplemental overlay is narrower still: it represents the reviewed entries that were matched, not every possible geriatric prescribing concern.

Keep the date of the source check with a missing-entry statement. A finding that a medicine was absent from an older version remains historically correct even if a later version adds it. Updating the evidence means adding the later finding with its provenance, not pretending the older document always contained it.

Missing information can guide the next question

An unavailable value can prompt a focused check of the ingredient, route, source version or original document. It can also expose a research gap that should be reported when a medication list is analyzed. Keeping that gap visible allows the next reviewer to improve the evidence without first undoing an invented zero.

References

1. Vennard O, Stewart C, Tolia M, Soiza RL, Myint PK. Anticholinergic Medication Burden Scales: A Systematic Review. J Am Geriatr Soc. 2026;74(6):1771-1784. Source
2. Chew ML, et al. Anticholinergic activity of 107 medications commonly used by older adults. J Am Geriatr Soc. 2008;56:1333-1341. Source
3. Carnahan RM, et al. The Anticholinergic Drug Scale as a measure of drug-related anticholinergic burden: associations with serum anticholinergic activity. J Clin Pharmacol. 2006;46:1481-1486. Source
4. Rudolph JL, et al. The anticholinergic risk scale and anticholinergic adverse effects in older persons. Arch Intern Med. 2008;168:508-513. Source
5. Boustani M, et al. Impact of anticholinergics on the aging brain: a review and practical application. Aging Health. 2008;4:311-320. Source
6. Lisibach A, Benelli V, Ceppi MG, et al. Quality of anticholinergic burden scales and their impact on clinical outcomes: a systematic review. Eur J Clin Pharmacol. 2021;77(2):147-162. Source
7. Jun K, Hwang S, Ah YM, Suh Y, Lee JY. Development of an Anticholinergic Burden Scale specific for Korean older adults. Geriatr Gerontol Int. 2019;19:628–634. doi:10.1111/ggi.13680. Source
8. UnifiedACB. Preserved public source-observation dataset, v3.0 RC12 final; inspected for this editorial revision. Source
9. American Geriatrics Society. 2023 updated AGS Beers Criteria for potentially inappropriate medication use in older adults. J Am Geriatr Soc. 2023;71:2052–2081. doi:10.1111/jgs.18372. Source

Disclosure

Funding: None. Conflict of interest: None declared for the UnifiedACB educational project.

Educational evidence summary. This content does not provide patient-specific medical advice and does not replace clinical judgment, medication reconciliation, or prescribing guidance.