Table 1

Equations for calculating post-test probabilities

Algorithm/parameters

Equations

Algorithm for sepsis

Pre-test probability_s

= prevalence of sepsis

Pre-test odds_s

= pre-test probability_s/(1 - pre-test probability_s)

Likelihood ratio_s

= exp(-8.2 + 0.85 × Ln [G-CSF_p] + 0.7 × Ln [IL-8_p])

Post-test odds_s

= likelihood ratio_s × pre-test odds_s

Post-test probability_s

= post-test odds_s/(1 + post-test odds_s)

Algorithm for pneumonia

Pre-test probability_vap

= prevalence of pneumonia

Pre-test odds_vap

= pre-test probability_vap/(1 - pre-test probability_vap)

Likelihood ratio_vap

= exp(-6.8 + 1.0 × Ln [G-CSF_t])

Post-test odds_vap

= likelihood ratio_vap × pre-test odds_vap

Post-test probability_vap

= post-test odds_vap/(1 + post-test odds_vap)

The concentrations of granulocyte colony-stimulating factor (G-CSF) and interleukin (IL)-8 used in the above equations are in pg/μl. Definitions of subscript abbreviations: p, plasma; s, sepsis; t, tracheal aspirate; vap, ventilator associated pneumonia.

Horisberger et al. Critical Care 2004 8:R443   doi:10.1186/cc2971