Appointment and step/size criteria as basis for classifying an outpatient Accuracy of a psychiatric case register

The aim of the study was to evaluate the accuracy of a local psychiatric case register in relation to outpatients, defined as patients with an appointment with the psychiatric service, to estimate the frequencies of false-positive and-negative outpatients in the register. Furthermore, the aim was to validate step/size criteria related to appointment criteria. The following criteria were used for appointment: a fixed appointment indicated that the patient had a new date for contact, and a drop-in-appointment that the patient may attend the psychiatric service without a new referral or screening procedure. The investigation was performed as a census study. Of the 197 patients with an appointment on the census day, 64.5% had a fixed appointment. The frequency of false negatives for fixed appointments was 5.5%, and for drop-in appointments 25.7%. Of the 198 registered patients on the census day, 26 (13.1%) were false positives. A step/size criterion defining an outpatient as a patient with at least one outpatient contact before and at least one after the census day and a maximum of 90 days between the contacts, resulted in a sensitivity of 49.2% and a predictive value of 93.3% related to appointment criteria. This criterion does not include the time span following a discharge until the date of the first ambulatory event in the outpatient episode or the time span after the last ambulatory event and a possible admission. If the criterion was extended to include this, the sensitivity was slightly higher (53.3%) and the predictive value slightly less (88.2%). A third criterion defining an outpatient as a patient with an ambulatory event within 90 days before the census day had a sensitivity of 86.8% and a predictive value of 63.3%.