Subgroup analysis according to population, continent and method of detection
| Studies (n) | Prevalence estimate, % (95% CI) | Heterogeneity test | ||||
| Χ2 | df | P values | I2 (%) | |||
| Population | ||||||
| Elderly | 6 | Median 5.08 (IQR 3.75–7.61) | 28.55 | 5 | <0.001 | 82.5 |
| General population | 17 | Median 4.42 (IQR 1.55–7.37) | 468.83 | 16 | <0.001 | 96.6 |
| Paediatric population | 1 | 3.42 (2.24 to 4.60) | NA | NA | NA | NA |
| Continent | ||||||
| North America | 8 | Median 7.17 (IQR 3.84–10.66) | 49.3 | 7 | <0.001 | 85.8 |
| Asia | 6 | Median 5.10 (IQR 1.54–7.61) | 231.98 | 5 | <0.001 | 97.8 |
| Europe | 7 | Median 4.42 (IQR 3.76–5.48) | 199.67 | 6 | <0.001 | 97.0 |
| Australia | 3 | 1.72 (0.93 to 2.52) | 3.19 | 2 | 0.203 | 37.2 |
| Method of detection | ||||||
| Combination methods | 21 | Median 4.42 (IQR 3.01–7.37) | 383.70 | 20 | <0.001 | 94.8 |
| A combination of medical record review and drug level analysis | 2 | 8.51 (3.95 to 13.07) | 3.71 | 1 | 0.054 | 73 |
| A combination of medical record review, drug level analysis and interview | 3 | 7.19 (5.11 to 9.26) | 0.19 | 2 | 0.911 | 0 |
| A combination of medical record review and interview | 15 | Median 3.76 (IQR 1.54–5.48) | 306.99 | 14 | <0.001 | 95.4 |
| A combination of medical record review, interview and pill count | 1 | 3.01 (1.87 to 4.15) | NA | NA | NA | NA |
| Single method | 3 | Median 4.15 (IQR 3.79–9.51) | 42.99 | 2 | <0.001 | 95.3 |
| Interview only | 1 | 3.79 (2.36 to 5.22) | NA | NA | NA | NA |
| Medical record review only | 2 | Median 6.83 (IQR 4.15–9.51) | 22.71 | 1 | <0.001 | 95.8 |
NA, not applicable.