Old data reveal that the sensitivity and positive predictive value of CRP > 35 mg/L for the diagnosis of pneumonia was 100%, and lower values were reported for bronchitis and bronchiolitis, while more recent data demonstrate that CRP ≥ 20 mg/L were linked to radiographic pneumonia, bacterial infection, and subsequent hospitalization, yet positive predictive values were too low to be of use in clinical practice. This evidence concerns the gene CRP and susceptibility to pneumonia measurement.