Table 3.
Attributable fractions (AF) and population attributable fractions (PAF) of fever to malaria by parasite density (dry season)
| Parasite density | Cases† | Controls‡ | |||||
|---|---|---|---|---|---|---|---|
| (/μL) | n | %¥ | n | %¥ | aOR | AF | PAF |
| 0 | 666 | 78 | 760 | 84 | 1 | ||
| 1-400 | 99 | 12 | 88 | 10 | 1.1 | 0.06 | |
| 401-4000 | 50 | 6 | 47 | 5 | 0.7 | 0£ | |
| 4001-40000 | 26 | 3 | 12 | 1 | 1.3 | 0.24 | |
| 40000+ | 11 | 1 | 1 | 0 | 7.0 | 0.86 | |
| Total | 852 | 908 | 0.11 | 0.02 | |||
† Cases: with fever, axillary temperature ≥ 37.5°C at hospital visit.
‡ Controls: without fever, axillary temperature < 37.5°C at hospital visit and no reported history of fever during the preceding 3 days.
¥ Percentage of patients in a certain parasite density class among cases/controls. aOR: odds-ratio (of fever at each stratum of parasite density, versus uninfected patients), adjusted for age; AF: attributable fraction, calculated as: 
;
£ (AF by definition ≥ 0)
PrevMal = % febrile patients with malaria infection
PAF: population attributable fraction, calculated as: PAF = AF(PrevMal).