CPIS was first proposed by Pugin and colleagues in Geneva in 1991 in mechanically ventilated ICU patients with suspected ventilator-associated pneumonia. They combined six readily available variables into a 0–12 point score and compared it with quantitative bronchoalveolar lavage cultures.

Evidence	Setting	Key points
Original derivation (Pugin 1991)	28 adults; 40 bronchoalveolar lavage procedures in a single mixed ICU.	Using a CPIS cut-off >6 with a bronchoalveolar lavage bacterial index ≥5, sensitivity for pneumonia was about 93% and specificity about 96–100%, but the cohort was small and the reference standard non-standard.
Single centre validation (Schurink 2004)	99 ventilated ICU patients with suspected VAP in the Netherlands.	With a modified CPIS cut-off >5, sensitivity was roughly 83% but specificity only 17%, area under the ROC curve about 0.55, and inter-observer agreement for CPIS ≤6 vs >6 was poor (kappa around 0.16).
Meta analysis (Shan 2011)	13 studies including 1,264 mechanically ventilated patients.	Across studies, pooled sensitivity for CPIS was about 65% and specificity about 64% for diagnosing VAP against quantitative cultures or histology, with diagnostic odds ratio around 4.8 and summary ROC area about 0.75, and substantial heterogeneity.
Guidelines (IDSA ATS 2016)	Adults with suspected HAP or VAP.	Recommends using clinical criteria alone, rather than CPIS plus clinical criteria, when deciding whether to start antibiotics, and advises against using CPIS to guide discontinuation of antibiotics.

CPIS therefore behaves as a semi-objective summary of clinical, radiographic and microbiology data; it cannot on its own reliably confirm or exclude ventilator-associated pneumonia.
Performance is particularly variable in trauma and burn cohorts, where injury-related inflammation and inhalation injury may raise scores without proven infection; lower airway quantitative cultures remain the preferred diagnostic reference where available.
Paediatric data are more limited and usually involve modified CPIS variants, so diagnostic performance should not be assumed to match adult ICU populations.
In practice, CPIS is best used to structure assessment and to follow response to therapy over time, alongside guideline based diagnostic criteria, chest imaging and respiratory microbiology.

Clinical Pulmonary Infection Score (CPIS) for Ventilator-Associated Pneumonia (VAP)