Validation of different techniques for the diagnosis of ventilator-associated pneumonia. Comparison with immediate postmortem pulmonary biopsy.

Abstract

To assess the accuracy of clinical parameters for the diagnosis of ventilator-associated (VA) pneumonia, as well as the diagnostic value of several invasive techniques, such as protected specimen brush (PSB), bronchoalveolar lavage (BAL), fiberoptic bronchial aspirates (FBAS), and percutaneous lung needle aspiration (PLNA), we compared the results of these techniques with the histopathology of immediate postmortem pulmonary biopsies, considered the "gold standard" reference test. We studied 30 mechanically ventilated patients (age 52 +/- 21 yr; mechanical ventilation period 9 +/- 7 days) who died in an intensive care unit. All patients received prior antibiotic treatment. The following procedures were performed immediately after death: bilateral PSB, BAL, FBAS, and PLNA, as well as bilateral minithoracotomies to obtain pulmonary biopsies as close as possible to the area sampled with the other techniques. According to the histopathology 18 patients had pneumonia and 12 did not. The presence of fever (sensitivity 55%, specificity 58%), purulent secretions (sensitivity 83%, specificity 33%), and chest radiograph infiltrates (sensitivity 78%, specificity 42%) could not differentiate in all instances presence from absence of pneumonia. Quantitative bacterial cultures of lung biopsies using 10(3) cfu/g as a cutoff point had low sensitivity (40%) and low specificity (45%) and could not differentiate the histologic absence or presence of pneumonia. Considering the histopathology of pulmonary biopsies as a gold standard, we found the following sensitivities for PSB, BAL, FBAS, and PLNA: 36, 50, 44, and 25%. The specificities were 50, 45, 48, and 79%, respectively. The sensitivities and specificities of different invasive techniques are much lower than those reported in clinical studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnostic investigation of ventilator-associated pneumonia using bronchoalveolar lavage: comparative study with a postmortem lung biopsy

“…Using small lung fragments of 1 x 1 x 1 cm, Chastre et al (17) found only a 23% rate of histologically defined VAP, probably due to the tiny specimen examined. However, other studies also using tiny lung fragments found higher frequencies of VAP, such as 55% (21), 60% (19), and 54% (present study). Whether our own prevalence was underestimated due to the size of the fragment examined is a matter of speculation, considering the 67% index found by Marquette et al (20) using bilateral pneumonectomy.…”

“…Only a few studies on humans using postmortem lung biopsy to assess the frequency of VAP have been published (17)(18)(19)(20)(21)(22)(23)(24)(25).…”

Diagnostic accuracy of protected catheter sampling in ventilator-associated bacterial pneumonia

“…Clinical diagnosis is commonly inaccurate in recognizing ventilator-associated bacterial pneumonia [3,27,28]. In the present work, all of the 14 patients with histologically proven ventilator-associated bacterial pneumonia showed the complete clinical picture of ventilatorassociated bacterial pneumonia before death compared with five of the 13 patients without histological evidence.…”

“…A complete clinical picture of pneumonia was defined as the presence of all the following criteria: chest radiograph showing a new and persistent infiltrate consistent with pneumonia, purulent sputum, elevated temperature >38.38C or white blood cells (WBCs) count $10,000 or #1,500 . mm 3 and alteration of gas exchange. A Clinical Pulmonary Infection Score (CPIS) was calculated during the 24 h preceding death according to the criteria of PUGIN et al [18].…”

“…An invasive strategy based on bronchoscopic sampling has been proposed by some authors [7±8] but this is time consuming, expensive and can worsen the patients' respiratory status. Moreover, some studies have highlighted the lack of sensitivity and/ or specificity [3,6,9]. A noninvasive strategy based on blind methods has also been proposed [9±11].…”