Bronchoalveolar lavage in the diagnosis of ventilator-associated pneumonia: to quantitate or not, that is the question.

Quantitative bronchoalveolar lavage (BAL) is used to diagnose ventilator-associated pneumonia (VAP). We prospectively compared semiquantitative (SQ) and quantitative (Qu) culture of BAL for VAP diagnosis. Ventilated patients suspected of VAP underwent bronchoscopic BAL. BAL fluid was examined by both Qu (colony-forming units [CFUs]/mL) and SQ culture (none, sparse, moderate, or heavy) and results were compared. VAP was defined as 105 CFU/mL or greater on Qu culture. Over 36 months, 319 BALs were performed. Sixty-three of 319 (20%) showed diagnostic growth by Qu culture identifying a total of 81 organisms causing VAP. All 63 specimens showed growth of some organism(s) on SQ culture with 79 of 81 causative organisms identified and two (Pseudomonas, one; Corynebacterium, one) not identified. The remaining 256 specimens did not meet the threshold for VAP by the Qu method. Among these, 79 did not show any growth on SQ culture. Among the 240 specimens showing some growth on SQ culture, a total of 384 organisms were identified. VAP rates in relation to strength of growth on SQ culture were: sparse, 10 of 140 (7%); moderate, 24 of 147 (16%); and heavy, 45 of 97 (46%). Sensitivity (Sn), specificity (Sp), positive (PPV), and negative (NPV) predictive values of SQ culture of BAL fluid for the diagnosis of VAP were 97, 21, 21, and 97 per cent, respectively. Nonquantitative culture of BAL fluid is fairly accurate in ruling out VAP (high Sn and NPV). It however has poor Sp and PPV and using this method will lead to unnecessary antimicrobial use with its attendant complications of toxicity, cost, and resistance.

Predictive value of broncho-alveolar lavage fluid Gram's stain in the diagnosis of ventilator-associated pneumonia: a prospective study.

BACKGROUND: Quantitative broncho-alveolar lavage (qBAL) is increasingly being used for diagnosing ventilator-associated pneumonia (VAP). The current study prospectively evaluates the accuracy of broncho-alveolar lavage fluid Gram's stain (GS) in predicting both the presence of VAP and the class of causative microorganism in patients suspected of VAP. METHODS: Patients suspected of VAP in a trauma or surgical intensive care unit underwent bronchoscopic qBAL with GS. Presence and class of organisms seen on GS were correlated respectively with the presence of VAP, as diagnosed by qBAL, and class of causative microorganism. VAP was defined as qBAL >10(5) colony forming units/mL. All data were gathered prospectively. RESULTS: During a 28-month study period, 229 patients underwent 309 qBALs for suspected VAP. Seventy-one (23%) specimens were positive for VAP (qBAL>10(5) CFU/mL). Fifty-four specimens (77%) had one causative microorganism, 13 (18%) had two, 3 (4%) had three, and 1 (1%) demonstrated four microorganisms giving a total of 93 VAPs. Forty-one (62%) of 66 specimens showing moderate or many microorganisms on GS were positive for VAP. However, 7 (4%) of 167 specimens showing none and 23 (30%) of 76 showing few microorganisms on GS were also positive for VAP. Of the 64 qBAL specimens positive for VAP and where the GS showed microorganisms, 6 (23%) of 26 showing only G+ microorganisms on GS had G- VAP (G- alone, 4; G+ and G-, 2), and 1 (8%) of 12 showing G- microorganisms only had G+ and G- VAP. Of the seven qBAL specimens positive for VAP where the GS did not show microorganisms, one had G+ and six had G- VAP. With the threshold of positivity of GS at more than none, the sensitivity, specificity, positive, and negative predictive values of GS for the presence of VAP were 90%, 67%, 45%, and 96% respectively. CONCLUSIONS: Broncho-alveolar lavage fluid GS is poor in predicting the presence of VAP and predicting the class of causative microorganism. Using GS to determine necessity of and to select class of antimicrobial therapy will result in delayed or inappropriate VAP therapy or both.

Subthreshold quantitative bronchoalveolar lavage: clinical and therapeutic implications.

BACKGROUND: Quantitative bronchoalveolar lavage (qBAL) is used for accurate diagnosis of ventilator-associated pneumonia (VAP). The current study aims at defining the incidence, outcomes and therapeutic implications of false-negative (FN) qBAL. METHODS: Ventilated trauma, surgery, and burn, patients suspected of VAP underwent bronchoscopic qBAL. VAP was defined as qBAL with >10(5) CFU/mL (threshold). To identify FN BALs, blood cultures drawn concomitant with BAL (+/-5 days of BAL) were analyzed. qBAL specimens growing <10(5) CFU/mL (subthreshold) with blood culture identifying the same organism, without any other source, were classified as FN. RESULTS: Over 39 months, 246 patients underwent 365 qBALs. Ninety-one specimens had no growth and 274 specimens grew 433 organisms--100 at threshold and 333 at subthreshold strength. Sixteen percent of threshold and 11% of subthreshold organisms were associated with bacteremia. Rates of bacteremia were similar across strengths of growth. Bacteremia at all strengths of growth was more common with Staphylococcal species (methicillin sensitive and resistant) and for hospital-acquired gram-negatives. Rates of bacteremia at all strengths of growth were significantly higher after the first week of hospitalization. Bacteremia worsened outcomes in both threshold group (higher mortality, p < 0.05) and subthreshold group (longer lengths of stay, p < 0.05). CONCLUSIONS: qBAL has 11% FN rate as measured by blood stream invasion. Propensity of blood stream invasion is related to species of organism (Staphylococcal species and hospital-acquired gram-negatives) and duration of hospitalization, but not to strength of growth. Isolation of these organisms in BAL, at any strength, after the first week should prompt strong consideration for antimicrobial therapy.

Correlation of manual dexterity with USMLE scores and medical student class rank.

INTRODUCTION: Surgical programs often rely on objective measures of medical school cognitive performance, including United States Medical Licensing Exams (USMLE) scores and class rank, to predict success of an applicant in their training program. Although job applicants in non-medical fields often undergo dexterity testing prior to being hired, this has not been widely used in the selection process for surgical residency applicants. Thus, successful identification of applicants likely to succeed in surgical fields remains elusive. Given this difficulty, we wondered if performance on tests of manual dexterity would correlate with USMLE board scores and medical school class rank. METHODS: Fourth year medical students underwent a clinical study of dexterity testing using the Stromberg Dexterity Test (gross motor), the O'Conner Tweezer Test (fine motor), and the MIST-VR laparoscopic simulator (Mentice Corporation, Gothenberg, Sweden). Performance times were compared with USMLE Step I & II scores and class rank, as well as a self-assessment of manual dexterity. RESULTS: A total of 113 medical students participated. Gross motor dexterity was significantly correlated with class rank (P = 0.04) and USMLE Step I score (P = 0.04). Fine motor dexterity and MIST-VR performance did not correlate with class rank or USMLE scores. Self-assessment of good manual dexterity correlated with faster performance times on the MIST-VR laparoscopic simulator (0.0174). CONCLUSIONS: Gross motor skill is associated with objective measures of medical school cognitive performance, such as class rank and USMLE scores. Furthermore, self-assessment of dexterity may predict baseline laparoscopic abilities. Further research is necessary to determine whether such dexterity testing could be helpful in identifying applicants who possess the ability to develop into competent surgeons.