Attributable Fraction Calculator

Calculate AFe, PAF and Prevented Fraction from 2×2 table

CasesControls
Exposed
Unexposed
Total00

Limits: max 2 rows, 2 columns, values up to 999,999,999

0.95%

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Enter 2×2 table data to calculate attributable fractions

Formula

Attributable Fraction (Exposed)

The attributable fraction in exposed (AFe) represents the proportion of disease in the exposed group that is attributable to the exposure:

AFe=RR−1RR=p1−p2p1AF_e = \frac{RR - 1}{RR} = \frac{p_1 - p_2}{p_1}

Or equivalently:

AFe=1−1RRAF_e = 1 - \frac{1}{RR}

Population Attributable Fraction (PAF)

PAF=Pe(RR−1)1+Pe(RR−1)PAF = \frac{P_e(RR - 1)}{1 + P_e(RR - 1)}

Where:

  • RR = relative risk
  • PeP_e = prevalence of exposure in population
  • p1p_1 = risk in exposed group
  • p2p_2 = risk in unexposed group