The authors investigated the link between patient characteristics, the Camberwell Assessment of Need Short Appraisal Schedule (cansas), early drop-out and treatment duration. Results showed that patients with severe mental illness (smi) who remained under treatment by an assertive community treatment team (N=611) were more frequently male, born outside the Netherlands and had a psychotic or addiction disorder more frequently than patients who had left the act team treatment early (N=430).
Table 1 (see below) shows that 62% of the patients born outside the Netherlands remained in treatment versus 38% drop-outs. That looks like a large 24% difference. However, patient characteristics were summarized in misleading row percentages.
The conclusion that patients who remained under treatment were more frequently born outside the Netherlands is based on 10% difference: 55% versus 45%. Proportions of drop-outs were even closer: 45% natives versus 38% of patients born outside the Netherlands. What looked like a 24% difference is only a 7% difference.
| In care | Drop out | |||
| Dutch | 272 | 221 | 493 | |
| Non-Dutch | 339 | 209 | 548 | |
| 611 | 430 | 1041 | ||
| Difference | ||||
| Column | 44,5% | 51,4% | 6,9% | |
| 55,5% | 48,6% | 6,9% | ||
| Row | 55,2% | 44,8% | 10,3% | |
| 61,9% | 38,1% | 23,7% | ||
The authors reported no effect sizes, but the link between ethnicity and drop-out can be expressed as an odds ratio: 1,32, 95% confidence interval: 1,03-1,69. This odds ratio is statistically significant, but that is no surprise when N=1041. Mulder and Kortrijk conclude that information on patient characteristics is important for the correct interpretation of routine outcome monitoring data. However, they failed to show the relevance of a 1,3 odds ratio.
Also see Mulder and Kortrijk need some benchmarking
