Trial setting and design
A 10-week, double-blind, randomized, placebo-controlled, parallel-group trial was performed at the outpatient clinics of Iran Psychiatric Hospital and Tehran Psychiatric Institute (affiliated with Iran University of Medical Sciences, Tehran, Iran) from April to December 2019.
Participants
Patients, aged 18–60 years, with a clinical diagnosis of OCD based on DSM-5 criteria, were screened for the study(24). Those with a diagnosis of moderate-to-severe OCD, defined by a Yale-Brown Obsessive Compulsive Scale (Y-BOCS) score of ≥ 21 were included(25, 26).
The patients attending the clinics were consecutively checked for the entry criteria and recruited until the sample size was achieved. All of the patients enrolled in the study were assessed with a structured clinical interview designed in accordance with the DSM-5 by an expert psychiatrist(24).
The exclusion criteria were: 1) the presence of life-threatening psychiatric symptoms (such as suicidal ideation); 2) comorbid axis I disorders; 3) serious medical or neurological conditions; 4) substance dependence (other than caffeine or nicotine); 5) intellectual disability (based on clinical judgment); 6) pregnancy/breastfeeding; 7) contraindication for the use of granisetron or sertraline; 8) history of the previous psychosurgery for OCD; 9) have a complete response with sertraline in their history. During the conduction of the trial, patients were not permitted to participate in any psychotherapeutic treatment. Furthermore, patients were excluded if they used any psychotropic drugs in the last 6 weeks (11, 12).
Interventions
Eligible participants were randomized to receive either granisetron, 1mg twice per day, or placebo for 10 weeks. All participants, regardless of group assignment, also received sertraline, 100 mg/day for 4weeks, and then gradually increased to 200mg/day. To minimize the side effects to the lowest level, the dosage of sertraline increased slowly every week.
Outcome
Y-BOCS was used for the assessment of patients at baseline and at weeks 0, 4, 8, and 10 of therapy. Y‐BOCS provides a rating scale for the severity of obsessive‐compulsive symptoms (11, 12). This clinician‐rated scale contains 10 questions, each item rated from 0 (no symptoms) to 4 (extreme symptoms)(26). The psychometric properties of the Persian version of Y‐BOCS are approved in previous studies(27–29).
The primary outcome of the trial was the difference of total score of the Y-BOCS among the two groups and between the baseline and the end of the trial. The secondary outcome measure was Y-BOCS compulsion and obsession subscale score changes between two groups during the trial period, and also the complete response, partial response, and remission rates, defined as ⩾35%, ⩾25% decrease in, and ⩽16 Y-BOCS total scores (30). Moreover, adverse effects were monitored every four weeks using a systematic questionnaire and three open questions to include any other side effects not included in the questionnaire (31–33). In case of observation of any serious adverse effects during the course of therapy, a physician assessed the potential role of the medication in inducing the adverse effects and omitted the patient from the trial. All missing outcome data have been imputed and did not include in the analysis.
Randomization, allocation, concealment, and blinding
Randomization of participants was conducted with a random permuted block method (ratio of 1:1 and blocks of four). The assigned group of each participant was printed consecutively and enveloped in similar in appearance. The allocation was not in reach of the participants or any outcome assessors. The statistical analyzer, randomizer, and outcome assessor each were separate individuals and were blinded to allocation. Also, granisetron and placebo tablets were similar in shape, color, size, and odor.
Sample size and statistical analysis
With a between-group difference of five points in Y-BOCS score, type I error of 5%, an effect size of 0.25, and power of 80%, using G-power 3.1.9.2 we calculated a sample size of 44 (22 in each group). Considering a drop-out rate of 30% (11, 12), our final sample size was calculated at 58 (29 in each group). IBM SPSS Statistic 23.0.0 (IBM Corporations, Somers, New York, USA) was used for the statistical analysis. Continuous variables were reported as mean±SD and categorical variables as n (%). Mean differences (MDs) between groups were reported as MDs (95% confidence interval (CI)). Fisher’s exact test, or χ2-test was used for the comparison among categorical variables. The independent samples t-test was conducted for the comparison of continuous variable values, respectively. The comparison of Y-BOCS total and subscale score changes in and between groups during the ten-week course of study was achieved by performing a two-factor, repeated-measure analysis of variance (ANOVA). Whenever sphericity of the data could not be assumed using the Mauchly’s test of sphericity, the Greenhouse-Geisser correction for degrees of freedom was used. Score changes from baseline in the participants of each group was examined using the paired sample t-test. A p-value level of ⩽0.05 was defined as significant. Missing data was imputed with last observation carried forward (LOCF) method.