IntroductionMinimum clinically important difference (MCID) is a measure that defines the minimum amount of change in an objective score of a clinical test that must be reached for that change to be clinically noticeable. We aimed to find the MCID for patients with predominantly negative symptoms of schizophrenia at its earliest occurrence.MethodsData of a 26-week long, double-blind study with 454 patients [Positive and Negative Symptom Scale Negative Factor Score (PANSS-FSNS) ≥24, Positive and Negative Symptom Scale Positive Factor Score (PANSS-FSPS) ≤ 19] treated with cariprazine 4.5 mg/d or risperidone 4 mg/d were analyzed. The Clinical Global Impression—Improvement scale was used to quantify minimum improvement (CGI-I = 3) and no clinical change (CGI-I = 4) on the PANSS-FSNS, and the MCID was estimated with the following methods: as the mean PANSS-FSNS changes corresponding to the first instance of minimal improvement across all visits (MCID1); as the difference between the PANSS-FSNS change associated with the first instance and the PANSS-FSNS changes associated with the last recorded clinically unchanged status across all visits (MCID2); with the effect size approach (MCID3); as the Youden Index based cut-off value between no clinical change and minimal improvement (MCID4); as the relative likelihood of minimal improvement (MCID5).ResultsThe MCID1 and MCID2 resulted in, respectively, a 3.8-point (18.5%) and a 1.5-point (7.3%) decrease from baseline severity on the PANSS-FSNS. Greater values were required for the MCID at later evaluation times. The cut-off between minimum improvement and no clinical change defined by the Youden Index was a−3-point (15%) change in the PANSS-FSNS. The effect size approach indicated the 1.5-point difference between minimally improved and unchanged patients to be a medium effect (ES = 0.6).ConclusionApplying different methods led to different results, ranging between 7.3 and 18.5% improvement from the baseline for the MCID at its earliest occurrence in patients with predominantly negative symptoms of schizophrenia.

The aim of this chapter is to summarize the state-of-the-art knowledge of clinical staging in schizophrenia spectrum disorders. Clinical staging has been introduced to psychiatry in the past two decades. Its primary goal is to divide the course of the disorder into recognizable stages based on seriousness, development and symptom characteristics in order to better predict prognosis and to adopt the most appropriate treatment strategies. The first staging model was developed in 1982. Since then several distinct concepts of clinical staging in psychiatry have emerged. To date, there is no clinical consensus regarding which staging model is the gold standard, nonetheless when merging them together an integrated staging concept arises. The integrated staging model of schizophrenia spectrum disorders is composed of four stages. The chapter will introduce the different staging models in a historical order as well as present the integrated staging model detailing the characteristics, timeline and dominating symptoms of each stage. Appropriate treatment strategies for the distinct stages will also be outlined.