A typical pre-requisite for CAT administration is the existence of an underlying item bank completely covering the range of the trait being measured. When a bank fails to cover the full range of the trait, examinees who are close to the floor or ceiling will often never achieve a standard error cut-off and examinees will be forced to answer items increasingly less relevant to their trait level. This scenario is fairly typical for many patients responding to patient reported outcome measures (PROMS). For IACAT 2017 ABSTRACTS BOOKLET 65 example, in the assessment of physical functioning, many item banks ceiling at about the 50%ile. For most healthy patients, after a few items the only items remaining in the bank will represent decreasing ability (even though the patient has already indicated that they are at or above the mean for the population). Another example would be for a patient with no pain taking a Pain CAT. They will probably answer “Never” pain for every succeeding item out to the maximum test length. For this project we sought to reduce patient burden, while maintaining test accuracy, through the reduction of CAT length using novel stopping rules.

We studied CAT administration assessment histories for patients who were administered Patient Reported Outcomes Measurement Information System (PROMIS) CATs. In the PROMIS 1 Wave 2 Back Pain/Depression Study, CATs were administered to N=417 cases assessed across 11 PROMIS domains. Original CAT administration rules were: start with a pre-identified item of moderate difficulty; administer a minimum four items per case; stop when an estimated theta’s SE declines to < 0.3 OR a maximum 12 items are administered.

Original CAT. 12,622 CAT administrations were analyzed. CATs ranged in number of items administered from 4 to 12 items; 72.5% were 4-item CATs. The second and third most frequently occurring CATs were 5-item (n=1102; 8.7%) and 12-item CATs (n=964; 7.6%). 64,062 items total were administered, averaging 5.1 items per CAT. Customized CAT. Three new CAT stopping rules were introduced, each with potential to increase item-presentation efficiency and maintain required score precision: Stop if a case responds to the first two items administered using an “extreme” response category (towards the ceiling or floor for the in item bank, or at ); administer a minimum two items per case; stop if the change in SE estimate (previous to current item administration) is positive but < 0.01.

The three new stopping rules reduced the total number of items administered by 25,643 to 38,419 items (40.0% reduction). After four items were administered, only n=1,824 CATs (14.5%) were still in assessment mode (vs. n=3,477 (27.5%) in the original CATs). On average, cases completed 3.0 items per CAT (vs. 5.1).

Each new rule addressed specific inefficiencies in the original CAT administration process: Cases not having or possessing a low/clinically unimportant level of the assessed domain; allow the SE <0.3 stopping criterion to come into effect earlier in the CAT administration process; cases experiencing poor domain item bank measurement, (e.g., “floor,” “ceiling” cases).