Volume 19, Number 9—September 2013
Research
New Estimates of Incidence of Encephalitis in England
Table 4
Sensitivity analysis adjusting for variation in positive predictive value for HES-only admissions*
| Positive predictive value, % | HES only | PHE study only | Both sources | Estimated total no. cases (95% CI) | % Completeness (95% CI) |
Estimated incidence | |
|---|---|---|---|---|---|---|---|
| HES† | PHE study | ||||||
| Encephalitis-specific code in any of the 20 diagnostic fields | |||||||
| 30 | 114 | 54 | 59 | 332 (272–391) | 52 (43–61) | 34 (27–41) | 3.42 |
| 40 | 152 | 54 | 59 | 405 (332–477) | 52 (43–61) | 28 (22–34) | 4.17 |
| 50 | 190 | 54 | 59 | 477 (392–562) | 52 (43–61) | 24 (18–29) | 4.91 |
| 54 | 206 | 54 | 59 | 508 (418–598) | 52 (43–61) | 22 (17–27) | 5.23 |
| 60 | 228 | 54 | 59 | 550 (452–648) | 52 (43–61) | 21 (16–25) | 5.67 |
| 70 | 266 | 54 | 59 | 623 (512–734) | 52 (43–61) | 18 (14–22) | 6.42 |
| 80 |
304 |
54 |
59 |
696 (572–819) |
52 (43–61) |
16 (12–20) |
7.17 |
| Encephalitis-specific code in primary field only | |||||||
| 30 | 71 | 60 | 53 | 265 (214–315) | 47 (38–56) | 43 (34–51) | 2.73 |
| 40 | 94 | 60 | 53 | 314 (254–374) | 47 (38–56) | 36 (28–44) | 3.23 |
| 50 | 117 | 60 | 53 | 363 (293–433) | 47 (38–56) | 31 (24–38) | 3.74 |
| 54 | 127 | 60 | 53 | 384 (310–458) | 47 (38–56) | 29 (23–36) | 3.96 |
| 60 | 141 | 60 | 53 | 414 (334–494) | 47 (38–56) | 27 (21–34) | 4.26 |
| 70 | 164 | 60 | 53 | 463 (374–553) | 47 (38–56) | 24 (19–30) | 4.77 |
| 80 | 188 | 60 | 53 | 514 (415–614) | 47 (38–56) | 22 (17–27) | 5.29 |
*Incidence = cases/100,000 population. HES, Hospital Episode Statistics; PHE, Public Health England
†Due to the Lincoln-Petersen formula, if the number of HES-only admissions varies, the total HES admissions (HES only plus matched) is proportional to the estimated total number of cases; hence, the completeness of HES (ratio) does not change with varying positive predictive value.
1On behalf of the United Kingdom Public Health England Aetiology of Encephalitis Study Group (members listed at the end of this article).
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