Outcomes for delusional infestation in multidisciplinary clinics

Delusional infestation (DI) is a psycho-dermatological illness that often presents to dermatologists. Patients have fixed delusional beliefs that they are infested with living or nonliving pathogens that cause symptoms. Antipsychotic medication is the treatment of choice. Patient engagement is a challenge. Little is known about the best settings in which to treat DI.

We examined outcomes for patients with DI referred to multidisciplinary clinics in the UK, comprising dermatologists or tropical medicine physicians paired with psychiatrists.

We used Clinical Global Impression scale (CGI-S) score changes as our main outcome parameter. We report average CGI-S score changes for all groups. We used independent t-tests and an Anova analysis to measure differences between those who had a planned discharge and those who were lost to follow-up (LTFU), separating each group between those who reported taking medication and those who did not.

Records from 465 patients were reviewed: 94 (20.2%) patients had no CGI-S data points (12.0% did not attend; 8.2% missing data); 151 (32.5%) were followed up and had a planned discharge; 193 (41.5%) were lost to follow-up (LTFU) at some point, of whom 63 patients (13.5%) attended only once and had their last (only) observation carried forward. Of the 281 (60.4%) patients who attended the clinics at least twice, 108 (38.4%) had a response or remission (n = 69; 24.6%). The mean average CGI-S score change was -1.29, indicating clinically relevant improvement. Those who had a planned discharge and reported to have taken medication had an average CGI-S score change of -2.02, indicating significant improvement. Those who took medication but were LTFU had an average CGI-S change of -0.63 (just below clinically relevant improvement); those LTFU who did not take medication did not improve (CGI-S change -0.07).

Patients with DI who took medication did significantly better than those who did not. Patients who had a planned discharge did significantly better than those who were LTFU. Multidisciplinary clinics have good clinical outcomes for patients with DI, especially where patient engagement was reasonable.