Introduction
Data and methods
Design and sample
Data collection and instruments
Predictive models
Statistical analysis
Results
Variable | Proxy for | Mean | SD | Min | Max |
---|---|---|---|---|---|
AGE (in years) | Age | 41.80 | 10.88 | 18.70 | 66.62 |
Multi-attribute EuroQol EQ-5D score | Utility | 0.76 | 0.26 | −0.43 | 1.00 |
SF-6D score | Health-related QoL | 0.71 | 0.13 | 0.30 | 1.00 |
Positive sub-score (PANSS_POS) | Symptoms severity | 11.71 | 5.13 | 7 | 35 |
Negative sub-score (PANSS_NEG) | Symptoms severity | 15.39 | 7.16 | 7 | 43 |
General psychopathology sub-score (PANSS_PSY) | Symptoms severity | 27.87 | 9.65 | 16 | 71 |
Calgary Depression Scale for Schizophrenia (CDSS, range from 1 to 27) | Depressive symptoms | 2.49 | 3.41 | 0 | 21 |
Global Assessment of Functioning (GAF, range 1–100) | Functioning | 52.04 | 15.66 | 0 | 99 |
Barnes Akathisia Scale (BAS, range 1–100) | Extra-pyramidal symptoms | 1.02 | 2.12 | 0 | 36 |
Variable | Proxy for | N | % | ||
---|---|---|---|---|---|
Proportion of males | Gender | 2593 | 63 | ||
Proportion of French patients | Country | 906 | 22 | ||
Proportion of German patients | 2099 | 51 | |||
Proportion of UK patients | 1111 | 27 | |||
Proportion of mixed antipsychotic | Antipsychotic type | 741 | 18 | ||
Proportion of only atypical | 1194 | 29 | |||
Proportion of only typical | 2181 | 53 |
Predictive model 1: using only the PANSS scores
EQ-5D | Coef. | Std. Err | z |
p > |z| | [95 % Conf. interval] | |
---|---|---|---|---|---|---|
Model 1 (PANSS score only) | ||||||
Constant term | 1.026055 | 0.0277925 | 36.92 | 0.000 | 0.971583 | 1.080527 |
PANSS_PSY | −0.0076876 | 0.0004386 | −17.53 | 0.000 | −0.0085473 | −0.006828 |
Sex | 0.0457537 | 0.0120427 | 3.80 | 0.000 | 0.0221504 | 0.0693569 |
Age | −0.0020646 | 0.0005313 | −3.89 | 0.000 | −0.0031059 | −0.0010233 |
Model 2 (PANSS score and additional covariates) | ||||||
Constant term | 1.011187 | 0.025353 | 39.88 | 0.000 | 0.9614961 | 1.060878 |
CDSS | −0.0192384 | 0.0011701 | −16.44 | 0.000 | −0.0215317 | −0.016945 |
PANSS_PSY | −0.0047262 | 0.0004566 | −10.35 | 0.000 | −0.005621 | −0.0038314 |
Age | −0.0023449 | 0.0004802 | −4.88 | 0.000 | −0.003286 | −0.0014038 |
Sex | 0.0322763 | 0.0108972 | 2.96 | 0.003 | 0.0109182 | 0.0536345 |
Predictive model 2: using additional covariates
Predictive models for the SF-6D
SF-6D | Coef. | Std. Err | z |
p > |z| | [95 % Conf. interval] | |
---|---|---|---|---|---|---|
Model 1 (PANSS score only) | ||||||
Constant term | 0.7958439 | 0.0073481 | 108.31 | 0.000 | 0.781442 | 0.8102459 |
PANSS_PSY | −0.0037952 | 0.0002124 | −17.86 | 0.000 | −0.0042115 | −0.0033788 |
Sex | 0.0243601 | 0.0058699 | 4.15 | 0.000 | 0. 0128554 | 0.0358648 |
Model 2 (PANSS score and additional covariates) | ||||||
Constant term | 0.8198619 | 0.0124882 | 65.65 | 0.000 | 0.7953856 | 0.8443382 |
CDSS | −0.009496 | 0.0005595 | −16.97 | 0.000 | −0.0105926 | −0.0083993 |
PANSS_PSY | −0.0021323 | 0.0002253 | −9.46 | 0.000 | −0.002574 | −0.0016907 |
BAS | −0.0040303 | 0.000773 | −5.21 | 0.000 | −0.0055454 | −0.0025152 |
Age | −0.0008743 | 0.0002373 | −3.68 | 0.000 | −0.0013394 | −0.0004092 |
Sex | 0.0139095 | 0.0053836 | 2.58 | 0.003 | 0.0033579 | 0.0244612 |
Measuring predictive ability and cross-validation
Dependent variable | Independent variables | Mean | Min | Max | Corr | RMSE | MAE |
---|---|---|---|---|---|---|---|
EQ-5D | Observed | 0.758 | −0.429 | 1 | 1 | 0 | 0 |
EQ-5D | Only PANSS | 0.752 | 0.369 | 0.907 | 0.321 | 0.246 | 0.182 |
EQ-5D | Only PANSSa
| 0.753 | 0.362 | 0.905 | 0.328 | 0.250 | 0.184 |
EQ-5D | Only PANSSb
| 0.755 | 0.367 | 0.924 | 0.316 | 0.248 | 0.182 |
EQ-5D | Only PANSSc
| 0.735 | 0.219 | 0.930 | 0.317 | 0.246 | 0.186 |
EQ-5D | Additional | 0.753 | 0.251 | 0.920 | 0.438 | 0.234 | 0.173 |
EQ-5D | Additionala
| 0.754 | 0.314 | 0.917 | 0.442 | 0.234 | 0.173 |
EQ-5D | Additionalb
| 0.753 | 0.230 | 0.919 | 0.439 | 0.235 | 0.174 |
EQ-5D | Additionalc
| 0.750 | 0.114 | 0.910 | 0.433 | 0.234 | 0.173 |
SF-6D | Observed | 0.707 | 0.301 | 1 | 1 | 0 | 0 |
SF-6D | Only PANSS | 0.704 | 0.514 | 0.775 | 0.328 | 0.119 | 0.098 |
SF-6D | Only PANSSa
| 0.706 | 0.552 | 0.774 | 0.342 | 0.119 | 0.098 |
SF-6D | Only PANSSb
| 0.702 | 0.552 | 0.773 | 0.342 | 0.119 | 0.097 |
SF-6D | Only PANSSc
| 0.703 | 0.512 | 0.765 | 0.325 | 0.120 | 0.098 |
SF-6D | Additional | 0.704 | 0.466 | 0.782 | 0.465 | 0.112 | 0.091 |
SF-6D | Additionala
| 0.708 | 0.441 | 0.788 | 0.454 | 0.112 | 0.092 |
SF-6D | Additionalb
| 0.703 | 0.422 | 0.785 | 0.457 | 0.112 | 0.091 |
SF-6D | Additionalc
| 0.706 | 0.399 | 0.786 | 0.466 | 0.112 | 0.092 |