Comparison of bronchoalveolar lavage and endotracheal aspirates culture sampling with clinical pulmonary infection score on diagnosis of ventilator-associated pneumonia

Aim

Ventilator-associated pneumonia (VAP) is a common cause of morbidity in ICU patients. There is still no evidence that invasive bronchoscopic techniques should form part of a routine approach to suspected VAP [1]. In our study, we compared specimen results in terms of sensitivity and specificity that were taken with bronchoalveolar lavage (BAL) fluid and endotracheal aspirates (ETA) and we examined the value of clinical pulmonary infection score (CPIS) in the diagnosis of VAP.

Materials and methods

The study included 50 adult patients in the ICU, who received mechanical ventilation for more than 48 hours, did not receive antibiotherapy and in whom VAP was clinically suspected. Patients who have contraindications for bronchoscopy were excluded. The VAP was defined by clinical criteria as follows: presence of a new or progressive lung infiltration on chest X-ray, plus at least two of the following clinical criteria; fever 380°C or 360°C, white blood cell count > 10,000 mm³ or < 5000 mm³, purulent ETA. Microbiologic sampling procedures were performed in patients using both distal tracheal suction and BAL. CPIS was calculated with a threshold value of 6, enabling identification of VAP patients.

Results

We determined BAL ≥ 10⁴ colony-forming units (cfu)/ml in all patients with ETA ≥ 10⁵ cfu/ml and exact conformity was achieved. We determined BAL ≥ 10⁴ cfu/ml, ETA were ≥ 10⁴ to < 10⁵ cfu/ml in 18 patients. Although ETA results were below the threshold level, they showed conformity with BAL results in 18 patients. We accepted BAL ≥ 10⁴ cfu/ml as a reference value of CPIS ≥ 6, and we determined sensitivity of 83% and positive predictive value of 50% during the diagnosis. When we accepted CPIS ≥ 6 as a reference value, the possibility of inaccurancy of diagnosis is high in every one of the two patients with VAP. Nearly one patient was missed in every five patients with VAP.

Conclusions

BAL results did not provide superiority in the diagnosis of VAP when compared with the ETA. A threshold level ≥10⁴ cfu/ml may be reduced for ETA and evaluation of CPIS alone is not suitable for diagnosis or exclusion of VAP.