br Patients and methods br Results Table
Patients and methods
Results Table 1 shows relevant demographic and clinical characteristics of the 123 patients in the cohort. BAL fluid samples were obtained at a median of 172.5 days after allo-HSCT (range 3 days to five years).
Discussion The definitive abandonment of traditional culture-based procedures for CMV testing in most laboratories and the non-availability of lung biopsy specimens for histopathological and immunohistochemistry examination make the diagnosis of proven or probable CMV pneumonia elusive nowadays. Moreover, no cut-off value for CMV DNA load in BAL fluid specimens discriminating between CMV pneumonia and pulmonary CMV DNA shedding in allo-HSCT recipients has been established at the present time. The assessment of the performance of quantitative CMV DNA s6 kinase testing for the diagnosis of CMV pneumonia faces several difficulties including: (i) the low incidence of this clinical event, (ii) the lack of a normalized procedure for CMV DNA PCR testing on BAL fluids, (iii) the non-negligible possibility of miscategorization of pneumonia cases as either being causally linked or unrelated to CMV when using BAL fluid specimens, or even lung tissue material, for CMV diagnosis, (iv) the persistence of a large variability of CMV DNA loads provided by different real-time PCR assays,31, 32– despite their calibration to the WHO International Standard for CMV DNA and, as already mentioned, (v) the relegation of virological procedures for CMV detection in clinical specimens. Inevitably, all these drawbacks were encountered in this study, so that we aimed not to establish a diagnostic cut-off, but rather to assess the range of CMV DNA loads quantifiable in BAL fluid specimens from patients in whom the causal involvement of CMV was highly unlikely or could be reasonably discarded; this, having in mind that we surely incurred CMV pneumonia infradiagnosis. Nevertheless, we perceived this limitation as not being an insoslayable obstacle to our purpose as: (i) CMV is unlikely to be the etiological agent of more than 10% of pneumonia cases among allo-HSCT recipients who undergo routine bronchoscopy, and (ii) survival of patients with CMV pneumonia who do not undergo specific anti-CMV treatment with appropriate doses of (val)ganciclovir or foscarnet is highly unlikely, provided the high rate of CMV pneumonia-associated mortality. We retrospectively reviewed clinical and microbiological data from patients who underwent routine quantitative CMV PCR testing on BAL fluid specimens at two transplant centers in our city. We deliberately chose not to include archived BAL specimens in our series because of the lack of data on the impact of cryopreservation on CMV DNA load quantitation in this sample type. Several findings arose from the present study. First, we confirmed previous observations– indicating that detection of CMV DNA in BAL fluid specimens using highly-sensitive PCR assays is a very common finding in allo-HSCT patients with pneumonia, irrespective of the definitive etiological diagnosis. In our series, CMV DNA was detected in more than one third of BAL fluid samples, the frequency of detection varying between 30% in patients seemingly with not having an infectious pneumonia and 45% in patients with mixed infections. In our series, recipient CMV seropositivity and treatment with corticosteroids were associated with detection of CMV in BAL fluid specimens. Of interest, the two patients with proven CMV pneumonia had CMV DNA detectable in BAL fluid. Second, we found a wide range of CMV DNA loads measured in BAL fluid specimens from patients with pneumonia in whom CMV causality was unlikely or reasonably ruled out attending to clinical (including therapeutic response to nonanti-CMV drugs), radiographic, lung autopsy histopathology or BAL fluid cytology (in some patients) and microbiological criteria. Interestingly, median CMV DNA loads were comparable irrespective of the nature and the number of co-detected microorganisms (at both participating centers), and were overall higher in the presence of concurrent DNAemia. As for the latter observation, in agreement with Boeckh et al., we found this not to be due to pulmonary hemorrhage (not shown). Overall, CMV DNA loads in BAL fluid specimens processed at HLF were of greater magnitude than those analyzed at HCU. Since CMV DNA loads produced by the Argene PCR assay are slightly lower than those measured by the Abbott PCR assay (not shown), differences in the net state of immunosuppression of patients at the time of BAL sampling across centers, as reflected by the immunodeficiency score index (higher for HLF patients), may account for this observation. In fact, a trend towards an inverse correlation was found between the ISI score and the CMV DNA load quantified in BAL specimens.