Abstract
Around a quarter of people who experience a first episode of psychosis (FEP) will develop treatment-resistant schizophrenia, but there are currently no established clinically useful methods to predict this from baseline. We aimed to explore the predictive potential for clozapine use as a proxy for treatment-resistant schizophrenia of routinely collected, objective biomedical predictors at FEP onset, and to validate the model externally in a separate clinical sample of people with FEP. We developed and externally validated a forced-entry logistic regression risk prediction model for clozapine treatment, or MOZART, to predict up to 8-year risk of clozapine use from FEP using routinely recorded information including age, sex, ethnicity, triglycerides, alkaline phosphatase levels and lymphocyte counts. We also produced a least-absolute shrinkage and selection operator (LASSO) based model, additionally including neutrophil count, smoking status, body mass index and random glucose levels. The models were developed using data from two United Kingdom (UK) psychosis early intervention services and externally validated in another UK early intervention service. Model performance was assessed by discrimination and calibration. We developed the models in 785 patients and validated them externally in 1,110 patients. Both models predicted clozapine use well during internal validation (MOZART: C statistic, 0.70 (95% confidence interval, 0.63–0.76); LASSO: 0.69 (0.63–0.77)). At external validation, discrimination performance reduced (MOZART: 0.63 (0.58–0.69); LASSO: 0.64 (0.58–0.69)) but recovered after re-estimation of the lymphocyte predictor (0.67 (0.62–0.73)). Calibration plots showed good agreement between observed and predicted risk in the forced-entry model. We also present a decision-curve analysis and an online data visualization tool. The use of routinely collected clinical information including blood-based biomarkers taken at FEP onset can help to predict the individual risk of clozapine use, and should be considered equally alongside other potentially useful information such as symptom scores in large-scale efforts to predict psychiatric outcomes.
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Data availability
The source data for this work is anonymized patient records from three UK NHS Trusts: the CPFT Research Database, SLaM CRIS and the Birmingham EIP. Data from these Trusts are only available to clinicians and clinical researchers with clinical contracts with the Trusts. The data are securely held on clinical systems and available following ethical approval to preserve patient confidentiality. Therefore, the raw data cannot be shared. However, we developed an online data visualization tool (https://eosimo.shinyapps.io/trs_app/) for both the original and recalibrated MOZART models, which allows interactive exploration of the effect of each predictor and their combinations on the risk of clozapine use based on the predictors included in this study.
Code availability
R code for data extraction and analysis is available upon request to the corresponding author.
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Acknowledgements
This work was funded by a Clinical PhD Fellowship to E.F.O. jointly funded by the NIHR Imperial BRC and the UK Research and Innovation Medical Research Council London Institute of Medical Sciences. B.I.P. acknowledges funding support from the NIHR (doctoral research fellowship, DRF-2018-11-ST2-018). R.U. received funding support from the NIHR (HTA grant 127700) and Medical Research Council (Therapeutic Target Validation in Mental Health grant MR/S037675/1). G.M.K. received funding support from the Wellcome Trust (grant 201486/Z/16/Z), the MQ: Transforming Mental Health (grant MQDS17/40), the Medical Research Council UK (grants MC_PC_17213; MR/S037675/1; and MR/W014416/1), and the British Medical Association Foundation (J Moulton grant 2019). R.N.C. acknowledges support from the Medical Research Council (grants MC_PC_17213, MR/W014386/1). This research was supported in part by the NIHR Imperial BRC and NIHR Cambridge BRC (BRC-1215-20014); J.P. and P.B.J. acknowledge funding from the NIHR ARC EoE; the views expressed are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health and Social Care. The funding bodies had no role in design or conduct of the study; collection, management, analysis or interpretation of the data; preparation, review or approval of the manuscript; or the decision to submit the manuscript for publication.
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E.F.O. and B.I.P. designed the study and selected the predictors and outcome variables under the supervision of R.U. and G.M.K., and with input from P.M., G.K.M., J.P., P.B.J., R.N.C. and O.D.H.; E.F.O. had access to all datasets, collected the data and performed the statistical analyses, in close discussion with B.I.P. and the wider supervisory team. M.P. and O.D.H. supported E.F.O. in data collection and analysis for the SLaM cohort. J.L. and R.N.C. supported E.F.O. in data collection and analysis for the Cambridge cohort. A.K. and R.U. supported E.F.O. in data collection and analysis for the Birmingham cohort. E.F.O. wrote the first draft of the manuscript, with constant support from B.I.P. All other authors contributed to the drafting, re-drafting and perfecting of the manuscript, including responses to reviewers’ comments.
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O.D.H. is a part-time employee of H. Lundbeck A/S. He has received investigator-initiated research funding from and/or participated in advisory/speaker meetings organized by Angelini, Autifony, Biogen, Boehringer Ingelheim, Eli Lilly, Heptares, Global Medical Education, Invicro, Janssen, H. Lundbeck A/S, Neurocrine, Otsuka, Sunovion, Recordati, Roche and Viatris/Mylan. O.D.H. has a patent for the use of dopaminergic imaging. R.N.C. consults for Campden Instruments and receives royalties from Cambridge Enterprise, Routledge and Cambridge University Press. The other authors declare no competing interests.
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Extended data
Extended Data Fig. 1 PubMed results for ‘risk AND prediction AND psychosis’ by year.
Generated with PubMed by Year. Available from http://esperr.github.io/pubmed-by-year/.
Extended Data Fig. 2 Internal validation: distribution of predicted probabilities for MOZART.
X axis: predicted probability.
Extended Data Fig. 3 Internal validation: distribution of predicted probabilities for the LASSO model.
X axis: predicted probability.
Extended Data Fig. 4 Internal validation: calibration plot for MOZART.
Model calibration is the extent to which outcomes predicted by the model are similar to those observed in the validation dataset. Calibration plots illustrate agreement between observed proportion (y axis) and predicted risk (x axis). Perfect agreement would trace the red line. Model calibration is shown by the continuous black line. Triangles denote grouped observations for participants at deciles of predicted risk, with 95% CIs indicated by the vertical black lines. Axes range between 0 and 0.3 since very few individuals received predicted probabilities greater than 0.3. N=785 participants in pooled development sample.
Extended Data Fig. 5 Internal validation: calibration plot for the LASSO model.
Model calibration is the extent to which outcomes predicted by the model are similar to those observed in the validation dataset. Calibration plots illustrate agreement between observed proportion (y axis) and predicted risk (x axis). Perfect agreement would trace the red line. Model calibration is shown by the continuous black line. Triangles denote grouped observations for participants at deciles of predicted risk, with 95% CIs indicated by the vertical black lines. Axes range between 0 and 0.3 since very few individuals received predicted probabilities greater than 0.3. N=785 participants in pooled development sample.
Extended Data Fig. 6 Internal validation: distribution of predicted probabilities for M3.
X axis: predicted probability.
Extended Data Fig. 7 Internal validation: calibration plot for M3.
Calibration plots illustrate agreement between observed proportion (y axis) and predicted risk (x axis). Perfect agreement would trace the red line. Model calibration is shown by the continuous black line. Triangles denote grouped observations for participants at deciles of predicted risk, with 95% CIs indicated by the vertical black lines. Axes range between 0 and 0.3 since very few individuals received predicted probabilities greater than 0.3. N=785 participants in pooled development sample.
Extended Data Fig. 8 Internal validation: distribution of predicted probabilities for M4.
X axis: predicted probability.
Extended Data Fig. 9 Internal validation: calibration plot for M4.
Calibration plots illustrate agreement between observed proportion (y axis) and predicted risk (x axis). Perfect agreement would trace the red line. Model calibration is shown by the continuous black line. Triangles denote grouped observations for participants at deciles of predicted risk, with 95% CIs indicated by the vertical black lines. Axes range between 0 and 0.3 since very few individuals received predicted probabilities greater than 0.3. N=785 participants in pooled development sample.
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Osimo, E.F., Perry, B.I., Mallikarjun, P. et al. Predicting treatment resistance from first-episode psychosis using routinely collected clinical information. Nat. Mental Health 1, 25–35 (2023). https://doi.org/10.1038/s44220-022-00001-z
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DOI: https://doi.org/10.1038/s44220-022-00001-z
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