A multiple imputation for missing neutrophil and CRP data was done. A backward logistic regression analysis included all signs and symptoms, duration of symptoms and categorized laboratory values. Duration of symptoms was used as a variable and an interaction term with categorized CRP values. Being a fertile aged woman (16–49 years old) was included as a variable and an interaction term for all signs and symptoms. Final step of backward stepwise logistic regression with multiple imputed pooled data resulted in statistically significant factors for construction of the score. Points for the score were obtained from regression coefficients by multiplying by 2 and rounding to the nearest integer. Please see Additional file 1 for a table of regression coefficients and the resulting points of the score.