Table 3.
Comparison of articles identified through Science Citation Index and PubMed searches until the end of 2003
| Search method(s) that identified article | PubMed and Science Citation Index (n = 31) | Science Citation Index only (n = 11) | PubMed only (n = 8) |
| Mean (s.d.) | 1999 (6.4) | 1996 (7.9) | 1997 (9.9) |
| Median (range) | 2002 (1969–2003) | 2001 (1982–2003) | 2001 (1973–2002) |
| Impact factor | |||
| Mean (s.d.)* | 4.2 (2.8) | 9.5 (9.8) | 3.9 (2.6) |
| Median (range) | 3.2 (1.1–10.5) | 3.8 (2.0–31.7) | 2.8 (1.3–7.6) |
| Study Type | 8 aetiologic 23 prognostic | 3 aetiologic 8 prognostic | 2 aetiologic 6 prognostic |
| Classification of outcome** | 25 positive 6 null | 5 positive 6 null | 6 positive 2 null |
| Sample size: aetiologic studies | |||
| Mean (s.d.) | 4502 (3331) | 5758 (4397) | 1101 (1089) |
| Median (range) | 3269 (76–9758) | 7217 (817–9239) | 1101 (332–1870) |
| Sample size: prognostic studies | |||
| Mean (s.d.) | 525 (626) | 832 (925) | 399 (441) |
| Median (range) | 344 (30–2885) | 552 (58–2320) | 288 (66–1250) |
* Four articles were published in journals with no impact factor (1 both methods, 1 Science Citation Index only, 2 PubMed only).
**Statistically significant result at the p < 0.05 level.