Ch. Marquette et al., DIAGNOSTIC-VALUE OF DIRECT EXAMINATION OF THE PROTECTED SPECIMEN BRUSH IN VENTILATOR-ASSOCIATED PNEUMONIA, The European respiratory journal, 7(1), 1994, pp. 105-113
Interpretation of the protected specimen brush (PSB) technique is base
d on quantitative bacterial cultures (QC), which unfortunately require
s at least 24 h. We prospectively compared the diagnostic value of dir
ect examination (DE) and QC of PSB specimens in 75 patients with suspe
cted pneumonia. We also determined the optimal technique for DE. QC wa
s performed using the serial dilution technique. From the original sus
pension, two cytospin slides were obtained and stained by the May-Grun
wald Giemsa (MGG) and the Gram method for DE. If the prescreening on t
he MGG-stained slide was positive, the morphology and the Gram stainin
g of the organisms were assessed on the Gram-stained slide. Using the
10(3) colony forming units (cfu.ml(-1)) threshold for defining PSB as
positive or negative, DE had a sensitivity of 85% and a specificity of
94%. In a parallel in vitro study, 18 pairs of PSB specimens were col
lected from respiratory secretions inoculated with S. aureus. From eac
h pah, one brush was processed as described above and the other was sm
eared on a glass slide prior to performance of QC. Using direct smear
instead of cytocentrifuged preparation, slightly but significantly aff
ected QC. Direct examination of cytospin slides is highly predictive o
f quantitative bacterial culture results, and provides rapid informati
on regarding the Gram-stain morphology of the causative organisms. It
may therefore guide initial therapy.