Epidemiology Assignment Questions

Below is a modified* forest plot from the systematic review looking at the clinical effects of risperidone for schizophrenia. The forest plot is looking at the outcome of “no clinically significant response in psychotic symptoms’ over a 12-week period. No clinically significant response was defined as a <20% decline in symptoms measured by either the PANSS (Positive and Negative Syndrome Scale) or the BPRS (Brief Psychiatric Rating Scale).

Figure 1. Comparison of Risperidone vs Placebo. Outcome of mental state: no clinically significant response in psychotic symptoms risperidone placebo Risk Ratio Risk Ratio Study Subgroup Events Total Events Total Weight M-H. Random 95% CI M-H. Random, 95% CI Bel 1991 19 53 34 51 10.6% Noguchi 1993 5 20 14 24 2.8% 0.43 (0.19.0.98) Reid 1994 26 61 48 61 16.2% 0.54 (0.39.0.75) Stanaway 1999 31 88 43 84 13.8% Webster 2007 50 89 77 97 30.3% 0.71 (0.57. 0.87) Worthington 2012 79 159 48 76 26.3% Total (95% CI) 470 393 100.0% Total events 210 264 Heterogeneity Tauf =0.01; Chif 14, df (P 0.29); 19% 0.2 0.5 Test for overal effect Z= =5.64(P<0.00001) Favours risperidone Favours placebo *This is a fictitious forest plot that has been modified slightly from the original systematic review. Based on your patient’s clinical history and examination, you have estimated that his baseline risk of having no improvement in his psychotic symptoms over the next 12 weeks without treatment is 75%

a) What do you estimate his risk of having no improvement in his psychotic symptoms in the next 12 weeks will be if he takes risperidone? (2 marks)

b) Based on your answer to a), what is the absolute change in risk of having no improvement if he decides to take risperidone? (2 marks)

Below is a forest plot from the same review that looks at the risk of extrapyramidal side effects when taking risperidone compared to placebo over a 12-week period.

Figure 2. Comparison of Risperidone vs Placebo. Adverse effects of extrapyramidal side effects risperidone placebo Risk Ratio Risk Ratio Study Subgroup Events Total Events Total Weight M-H, Random, 95% a Year M.H. Random, 95% CI Bell 1991 18 153 10 151 28.8% 1.78(0.85.3.72) 1991 Reid 1994 19 144 7 149 23.1% 2.81(1.22.6.48) 1994 Webster 2007 6 24 5 24 15.3% 1.20(0.42.3.41) 2007 Worthington 2012 13 53 12 54 32.9% 1.10.0.56.2.19) 2012 Total (95% CII) 374 378 100.0% Total events 56 34 Heterogeneity: Tau =0.02 3.29, =0.35); 0.2 0.5 Test for overal effect (=217(P=0.03) Favours risperidone Favours placebo You have estimated that the baseline risk of your patient having any extrapyramidal type symptoms without this medication over the next 12 weeks is 10%

c) What do you estimate his risk of experiencing an extrapyramidal side effect over the next 12 weeks would be if he takes risperidone? (2 marks)

d) Based on your answer to b), what is the absolute change in terms of risk of these harms? (2 marks)