Available online at www.sciencedirect.com
Diagnostic Microbiology and Infectious Disease 68 (2010) 132 – 139
www.elsevier.com/locate/diagmicrobio
Mycology
Clinical utility and prognostic value of bronchoalveolar lavage
galactomannan in patients with hematologic malignancies☆
Me-Linh Luonga,b , Charles Filionb , Annie-Claude Labbéb , Jean Royc , Jacques Pépind ,
Julia Cadrin-Tourignyb , Stéphane Carignane , Donald C. Shepparda , Michel Laverdièreb,⁎
a
Department of Microbiology, McGill University Health Center, Montreal, Quebec H3A 2B4, Canada
Department of Microbiology, Hôpital Maisonneuve-Rosemont, Université de Montréal, Montreal, Quebec H1T 2M4, Canada
c
Division of Hemato-Oncology, Department of Medicine, Hôpital Maisonneuve-Rosemont, Université de Montréal, Montreal, Quebec H1T 2M4, Canada
d
Department of Microbiology and Infectious Diseases, Université de Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada
e
Department of Radiology, Hôpital Maisonneuve-Rosemont, Université de Montréal, Montreal, Quebec H1T 2M4, Canada
Received 10 February 2010; accepted 24 March 2010
b
Abstract
We conducted a single-center retrospective cohort study to determine the performance characteristics of the galactomannan (GM) assay in
bronchoalveolar lavage (BAL) in patients with hematologic malignancies. Patients were classified as proven, probable, possible, or no
invasive pulmonary aspergillosis (IPA), according to international guidelines. A total of 173 BAL samples from 145 patients were included.
There were 5 proven, 7 probable, and 35 possible cases of IPA. Using a GM index cutoff of ≥0.5, the sensitivity, specificity, and positive and
negative predictive values (PPV and NPV, respectively) of the BAL GM assay were 100%, 78%, 26%, and 100%, respectively. Using a GM
index cutoff of ≥2.0, the sensitivity and NPV remained 100%, but specificity and PPV increased to 93% and 50%, respectively. The BAL
GM assay is a highly sensitive screening test for IPA in patients with hematologic malignancies. Increasing the cutoff value to 2.0 would
improve the performance of this assay.
© 2010 Elsevier Inc. All rights reserved.
Keywords: Aspergillosis; Galactomannan; Bronchoalveolar lavage; Hematologic malignancies
1. Introduction
Invasive pulmonary aspergillosis (IPA) is an important
cause of morbidity and mortality in patients with hematologic malignancies and in hematopoietic stem cell transplant
(HSCT) recipients (Fukuda et al., 2003; Garcia-Vidal et al.,
2008; Labbe et al., 2007; Marr et al., 2002). The high
mortality rate stems in part from the inability to make an
early and reliable diagnosis (Denning et al., 1997; Levy
et al., 1992). Recently, galactomannan (GM) aspergillus
antigen detection in the serum has been introduced as an
adjunctive diagnostic test to assist diagnosis of IPA in HSCT
☆
Presentation preliminary findings of this study were presented at the
19th European Conference of Clinical Microbiology and Infectious
Diseases, Helsinki, Finland, May 2009, and at the 26th International
Congress of Chemotherapy, Toronto, Canada, June 2009.
⁎ Corresponding author. Tel.: +1-514-252-3817; fax: +1-514-252-3898.
E-mail address: [email protected] (M. Laverdière).
0732-8893/$ – see front matter © 2010 Elsevier Inc. All rights reserved.
doi:10.1016/j.diagmicrobio.2010.03.017
recipients. The sensitivity of GM antigen detection in serum
remains limited, ranging between 61% and 89% (Leeflang
et al., 2008; Pfeiffer et al., 2006).
In an attempt to improve sensitivity of diagnostic tests for
IPA, several authors have investigated the utility of GM
antigen detection in bronchoalveolar lavage (BAL) specimens (Becker et al., 2003; Clancy et al., 2007; Husain et al.,
2007; Klont et al., 2004; Maertens et al., 2009; Meersseman
et al., 2008; Musher et al., 2004; Nguyen et al., 2007; Penack
et al., 2008; Sanguinetti et al., 2003; Siemann and KochDorfler, 2001; Verweij et al., 1995). These results have been
promising, with sensitivities ranging from 60% to 100%
(Clancy et al., 2007; Husain et al., 2007). Consequently, the
detection of GM in BAL has been recently added to the
revised definitions of invasive fungal diseases in a consensus
statement by the European Organization for Research and
Treatment of Cancer and the National Institute of Allergy
and Infectious Diseases Mycoses Study Group (EORTC/
MSG) (De Pauw et al., 2008). However, no cutoff value for
M.-L. Luong et al. / Diagnostic Microbiology and Infectious Disease 68 (2010) 132–139
positivity has been provided, and the existing data on the
performance characteristics of this test remains limited.
In particular, data pertaining to the high-risk hematology
population are limited (Becker et al., 2003; Maertens et al.,
2009; Musher et al., 2004; Penack et al., 2008; Salonen et al.,
2000; Sanguinetti et al., 2003; Verweij et al., 1995). The
reported performance of the BAL GM in this population has
been inconsistent, with sensitivity varying from 76% to 100%.
This variability may be related to a number of factors including
patient characteristics (Herbrecht et al., 2002), differences in
cutoff values (Herbrecht et al., 2002), antigen deterioration
from prolonged storage (Musher et al., 2004), antifungal
therapy (Becker et al., 2003), and most importantly, use of
heterogeneous definitions of IPA resulting in misclassification
(Becker et al., 2003; Musher et al., 2004; Verweij et al., 1995).
The primary objective of this study was therefore to
assess the performance characteristics of the GM assay in
BAL specimens for diagnosing IPA in a large cohort of
patients with hematologic malignancies. In addition, we
examined the performance of this test using different cutoff
values for positivity. Finally, we evaluated the prognostic
value of a positive BAL GM in this high-risk population.
2. Materials and methods
2.1. Study population
We conducted a retrospective cohort study among
patients with hematologic malignancies treated at Hôpital
Maisonneuve-Rosemont, Montreal, Quebec, Canada, a 725bed tertiary care university center accredited by the
Foundation for Accreditation of Cellular Therapy in
Montreal, Canada. Between March 2005 and April 2008,
all adult patients with hematologic malignancies or HSCT
presenting respiratory symptoms or radiology abnormalities
and neutropenia ≤0.5 × 109/L, requiring endotracheal
intubation, triple immunosuppression for treatment of
graft-versus-host disease, or community-acquired pneumonia not responding to appropriate oral antibiotics were
evaluated with BAL. All HSCT recipients and patients with
hematologic malignancies were followed by the same team
of physicians during their entire treatment. Patients without a
thoracic computed tomography (CT) scan performed within
30 days of BAL were excluded as this is required for
EORTC/MSG clinical criteria. For patients with multiple
positive GM BAL, only the first positive BAL was
considered for analysis to avoid inclusion of subsequent
GM BAL results from an already diagnosed IPA. Subsequent positive BAL GM were excluded from analysis to
prevent repeated inclusion of the same case of IPA. The
study was approved by our institutional ethics committee.
2.2. Bronchoscopy
Bronchoscopy was performed using flexible fiberoptic
bronchoscope following mild sedation and local anesthesia
133
with xylocaine 2%. Sterile isotonic saline was instilled in two
to four 50-mL aliquots up to a volume of 200 mL, with
immediate aspiration after each aliquot, and was immediately
sent to the pathology and microbiology laboratories. BAL
samples were analyzed for cytology (including Pneumocystis
jiroveci), Gram, calcofluor white fungal, and auramine
mycobacterial stains and cultured for aerobic bacteria
(including Legionella), fungi, viruses, and mycobacteria.
2.3. Platelia GM enzyme immunoassy assay
The GM assay was performed on uncentrifuged BAL
specimens according to the manufacturer's recommendations for testing on serum (Bio-Rad, Edmonds, WA). The
assay was run twice weekly in the routine microbiology
laboratory. Samples were stored at 2 to 8 °C according to
recommendations for serum samples. For the initial analysis,
an index cutoff value of 0.5 was chosen as the threshold for
positivity, as suggested by the manufacturer for sera. All
results with an index ≥0.5 were repeated on the same
specimen before being considered as positive. Results were
reported to the attending physician. The assay was also used
on sera as requested by the attending physician. As serum
GM was not systematically obtained on all patients, its result
was considered in this study only when performed within
7 days from the BAL.
2.4. Case definitions
Retrospective chart review was performed for collection
of clinical information, laboratory results, and radiologic
reports. Antibiotic and antifungal use was recorded if
administered within 2 days prior to BAL. Each patient was
classified as having proven, probable, possible, or no IPA
using the revised definitions of invasive fungal disease from
the EORTC/MSG Consensus Group (De Pauw et al., 2008).
In brief, proven IPA required histopathologic demonstration
of fungal elements in involved tissues or positive culture
from a normally sterile body site. Probable IPA required the
presence of at least 1 host factor (neutrophils b0.5 × 109/L
for more than 10 days, allogeneic HSCT, prolonged use of
corticosteroids at a minimum dose of 0.3 mg/kg a day of
prednisone equivalent for N3 weeks, treatment with
immunosuppressive medication such as cyclosporine, specific monoclonal antibodies, or nucleoside analogue within
the last 90 days), clinical features (dense, well, circumscribed
lesion with or without halo sign, air crescent sign or cavity on
thoracic CT scan), and mycological evidence of infection
(positive fungal culture from sputum or BAL, GM antigen
detection in serum). Cases that met both host factor and
clinical criteria, but for which mycological criteria were
absent, were classified as possible IPA. All other patients
were considered not to have IPA. Although the BAL GM is
included in the mycological criteria for probable IPA, it was
not considered as a criterion to classify cases in order to
avoid an incorporation bias. All cases with alternative
diagnoses were classified as without IPA. For performance
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M.-L. Luong et al. / Diagnostic Microbiology and Infectious Disease 68 (2010) 132–139
Table 1
Patient characteristics for each 173 BAL specimens (145 patients),
according to BAL GM assay result (index cutoff ≥0.5)
Total n (%) GM + n (%) GM − n (%)
Mean age (years)
55
Male sex
113 (65)
HSCT recipients
122 (71)
Allogeneic
88 (51)
Autologous
34 (20)
Hematologic malignancies
51 (29)
Acute myelogenous leukemia
20 (12)
Acute lymphoblastic leukemia
9 (5)
Non-Hodgkin's lymphoma
9 (5)
13 (8)
Othersa
38 (22)
Neutropenia ≥10 daysb
Graft-versus-host disease
54 (31)
(acute or chronic)
Steroid use in past 2 monthsc
85 (49)
T-cell immunosuppressives
77 (45)
β-Lactam antibioticsd
108 (62)
Piperacillin–tazobactamd
26 (15)
Mold-active antifungal therapye 65 (38)
54
30 (64)
38 (81)
31 (66)
7 (15)
9 (19)
6 (13)
2 (4)
1 (2)
0 (0)
14 (30)
22 (47)
55
83 (66)
84 (66)
57 (45)
27 (21)
42 (33)
14 (11)
7 (6)
8 (6)
13 (10)
24 (19)
32 (25)
27 (57)
28 (60)
35 (75)
9 (19)
24 (51)
58 (46)
49 (39)
73 (58)
17 (13)
41 (32)
All data are no. (%) of patients unless otherwise indicated.
a
Multiple myeloma, aplastic anemia, Hodgkin's lymphoma, and
chronic lymphocytic leukemia.
b
Neutrophils count b0.5 × 109 neutrophils/L.
c
Prednisone, 0.3 mg/kg a day, equivalent for N3 weeks.
d
Antibiotics received within 2 days prior to bronchoscopy.
e
Voriconazole, itraconazole, caspofungin, amphotericin B, and
liposomal amphotericin B, within 2 days prior to bronchoscopy.
analysis, proven and probable IPA were grouped together
as IPA.
2.5. Statistical analysis
Data were analyzed with Stata 10.0 (Stata, College
Station, TX). Proportions were compared with the χ2 test or
Fisher's exact test when numbers were small. Sensitivity,
specificity, and positive and negative predictive values (PPV
and NPV, respectively) were calculated on a per-episode
basis for BAL. Receiver operating characteristic (ROC)
analysis was performed to illustrate the association between
BAL GM index result and IPA (proven or probable). To
assess the prognostic value of BAL GM on all-cause
mortality within 60 days of BAL, we used Cox regression
to calculate crude and adjusted hazard ratios along with their
95% confidence intervals (CIs).
3. Results
During the study period, 216 BAL samples from 156
patients were tested for GM. Forty-three BAL samples were
excluded from our analysis due to absence of a thoracic CT
scan performed within 30 days of BAL (n = 10) or because of
a prior positive BAL GM result (n = 33). In total, 173 BAL
samples from 145 patients were included in our cohort.
Paired serum GM samples were available in 124 patients.
Study population characteristics are shown in Table 1.
Characteristics found more frequently in patients with a
positive BAL GM include presence of graft-versus-host
disease (47% versus 25%, P = 0.007), T-cell immunosuppressive therapy (60% versus 39%, P = 0.01), β-lactam
antibiotic use (74% versus 58%, P = 0.04), and mold-active
antifungal therapy within 2 days prior to bronchoscopy (50%
versus 32%, P = 0.02).
Overall, we identified 5 cases of proven IPA and 7 cases
of probable IPA (total of 12 cases of IPA); 36 BAL samples
were obtained from 28 patients with possible IPA and 125
from 105 patients with no IPA (total of 161 BAL samples
from 133 patients without IPA). Despite fulfilling host
factors clinical and microbiologic criteria, 1 patient was
classified as without IPA, given the presence of an
alternative diagnosis (nocardiosis). Four patients presenting
host factors and a positive aspergillus culture (without
meeting the clinical criteria on CT scan) were classified as
without IPA.
Using a GM index cutoff value of ≥0.5, we obtained 47
positive and 126 negative BAL GM samples, yielding a
sensitivity and specificity of 100% and 78%, respectively,
and a PPV and NPV of, 26% and 100% (Table 2). In
contrast, microscopy and culture had a sensitivity of 58%
and 75%, respectively (Table 2). All 12 patients with
probable or proven IPA had a paired serum GM samples;
Table 2
Performance characteristics for diagnosis of proven or probable IPA by the revised EORTC/MSG definitions (n = 173)
Test (no. of positive samples) (%)
Sensitivity (95% CI) (%)
Specificity (95% CI) (%)
PPV (95% CI) (%)
NPV (95% CI) (%)
BAL GM index cutoff
≥0.5 (47, 27%)
≥1.0 (38, 22%)
≥1.5 (29, 17%)
≥2.0 (24, 14%)
≥2.5 (23, 13%)
≥3.0 (21, 12%)
≥3.5 (17, 10%)
BAL microscopy (11, 6%)
BAL culture (19, 11%)
Serum GM ≥0.5 (10, 8%)a
100 (73.5–100)
100 (73.5–100)
100 (73.5–100)
100 (73.5–100)
100 (73.5–100)
100 (73.5–100)
83 (51.6–97.9)
58 (27.7–84.8)
75 (42.8–94.5)
58 (27.7–84.8)
78 (71.1–84.4)
84 (77.9–89.7)
89 (82.9–93.2)
93 (88.1–96.5)
94 (88.9–97.0)
94 (89.7–97.4)
96 (91.2–98.2)
98 (93.7–99.3)
94 (88.9–97.0)
97 (92.4–99.4)
26 (13.9–40.3)
32 (17.0–49.8)
40 (22.7–59.4)
52 (30.6–73.2)
55 (32.2–75.6)
57 (34.0–78.2)
59 (32.9–81.6)
64 (30.7–89.1)
47 (24.4–71.1)
70 (34.8–93.3)
100 (97.1–100)
100 (97.3–100)
100 (97.4–100)
100 (97.6–100)
100 (97.6–100)
100 (97.6–100)
99 (95.4–99.8)
97 (92.9–99.0)
98 (94.4–99.6)
96 (90.1–98.6)
a
Serum GM were included in the analysis if performed within 7 days of the BAL (n = 124).
M.-L. Luong et al. / Diagnostic Microbiology and Infectious Disease 68 (2010) 132–139
135
Fig. 1. Distribution of the BAL GM assay index value according to the EORTC/MSG definitions for IPA1.
1
Patients were considered on mold-active antifungal if they received voriconazole, itraconazole, caspofungin, amphotericin B, or liposomal amphotericin B
within 2 days of the bronchoscopy.
only 7 had a positive result, yielding to a sensitivity of
58%. Specificity was high (97%). The BAL GM index
value for proven and probable IPA varied between 3.0 and
8.8, whereas the BAL GM index value for false-positive
results varied between 0.59 and 7.14 (Fig. 1). ROC analysis
(Fig. 2) found that a cutoff value of 3.0 provided the same
sensitivity of 100% and a marginally higher specificity of
94% (Table 2).
Fig. 2. ROC curve for BAL GM index results.
136
M.-L. Luong et al. / Diagnostic Microbiology and Infectious Disease 68 (2010) 132–139
Using a GM index cutoff value ≥0.5, we found 35 falsepositive BAL results. Of these, 15 occurred in the group with
possible IPA and 20 in the group without evidence of IPA.
Table 3 shows alternative diagnoses in patients with falsepositive results, based on clinical presentation, microbiologic
cultures, histopathology, or other specific investigations.
Nine (26%) patients had a clinical diagnosis of IPA and were
treated by the attending physicians accordingly, despite not
fulfilling the EORTC/MSG criteria for proven or probable
IPA. As β-lactam antibiotics have been reported to cause
false-positive GM results, we examined this variable as well
(Bart-Delabesse et al., 2005). Of all false-positive BAL GM
results, 28 (80%) occurred among patients receiving
β-lactam antibiotics, including 8 patients (23%) on piperacillin–tazobactam.
Sixty-five (38%) samples of BAL were obtained from
patients who had received mold-active antifungal therapy
within 2 days prior to bronchoscopy. Positive BAL GM
samples occurred more frequently in patients receiving
mold-active antifungals (n = 24, 37%) than in those without
(n = 23; 21%; odds ratio, 2.16; 95% CI, 1.09–4.28), with
BAL GM indices significantly higher in patients treated with
mold-active antifungal therapy (mean BAL GM index, 0.4)
than in those who were not receiving a mold-active
antifungal therapy at the time of BAL (mean GM index,
0.2; P = 0.025).
Twenty-five (17%) patients died within 60 days of first
BAL sample collection. Those who died had a higher index
of BAL GM (mean of 2.0) when compared to patients who
survived (mean of 0.7, P = 0.0004). As shown in Table 4, a
BAL GM index values from 0.5 to 1.99 were not associated
with a higher 60-day mortality risk compared to patients with
a BAL GM lower than 0.5. However, a BAL GM index
value ≥2.0 was significantly associated with a higher 60-day
mortality risk compared to patients with a BAL GM lower
than 0.5. Other factors associated with an increased risk of
death included acute myelogenous leukemia, neutropenia
within 10 days before BAL, and use of mold-active
antifungal within 2 days of bronchoscopy. Age, HSCT
(autologous or allogeneic), graft-versus-host disease, T-cell
immunosuppressive therapy, and steroids use in previous
2 months were not associated with an increased risk of death.
In multivariate analysis, a BAL GM index value ≥2
remained an independent risk for death. Acute myelogenous
leukemia and mold-active antifungal use prior to bronchoscopy also remained significantly associated with a 60-day
mortality risk.
4. Discussion
The results of this large cohort study highlight that the
BAL GM has superior sensitivity for the diagnosis of IPA
compared to conventional diagnostic methods. The sensitivity of the BAL GM was 100% (regardless of whether a
cutoff of 0.5, 2.0, or 3.0 was used) as compared to 58%,
75%, and 58% for BAL fungal microscopy, fungal culture,
and serum GM detection, respectively. Therefore, a
negative BAL GM strongly suggests the absence of IPA.
This high sensitivity is, however, obtained at the expense of
a reduction in specificity. Using a cutoff value of 0.5, we
obtained a high rate of false-positive results. Twenty-four
patients (69%) with false-positive BAL GM results had an
alternate clinically important disease such as pulmonary
nocardiosis, cryptococcosis, or recurrent lymphoma. Without further workup, these diagnoses would have been
missed. Consequently, a positive result with this cutoff is
insufficient to confirm the diagnosis of IPA and commands
further investigation.
Among patients with false-positive BAL GM, 9 (26%) were
diagnosed with clinical IPA by their physician. All presented
clinical risk factors for IPA had a highly positive GM index in
the BAL and 4 had a positive BAL culture for Aspergillus sp.
All presented abnormal radiologic findings; however, these
findings did not fulfill the EORTC/MSG radiologic criteria of
typical nodule, cavity, or halo sign. Although angioinvasive
IPA classically produces these aforementioned radiologic
abnormalities, airway-invasive IPA can produce different
radiologic abnormalities such as peribronchiolar consolidation,
centrolobular micronodules (b5 mm), ground-glass attenuation,
Table 3
Alternative diagnoses in patients with false-positive BAL GM assay results (n = 35)
Alternative diagnosis
a
Clinical diagnosis of IPA
Bacterial pneumonia
Nocardia infection
Cryptococcus infection
Drug-induced pneumonitis
Hematologic malignancy (lymphoma or chloroma)
Pulmonary GVHD
BOOP
Atelectasis
No diagnosis
Total (%)
No IPA
Possible IPA
Mean GM index value (range)
β-Lactam Abx (%)
PTZ (%)
9 (26)
12 (36)
2 (6)
1 (3)
1 (3)
4 (12)
1 (3)
2 (6)
1 (3)
2 (6)
2
10
1
1
1
3
1
1
0
0
7
2
1
0
0
1
0
1
1
2
3.35 (1.1–7.1)
2.5 (0.6–5.8)
0.9 (0.5–1.3)
0.9
0.6
0.8 (0.6–1.2)
3
1.9 (0.6–3.3)
1.8
4.0 (1.5–6.5)
6 (67)
10 (83)
2 (100)
1 (100)
1 (100)
3 (75)
1 (100)
1 (50)
1 (100)
2 (100)
0 (0)
2 (20)
1 (50)
0 (0)
0 (0)
2 (50)
1 (100)
0 (0)
1 (100)
1 (50)
GVHD = graft-versus-host disease; BOOP = bronchiolitis obliterans organizing pneumonia; Abx = antibiotics; PTZ = piperacillin–tazobactam.
a
Diagnosis of IPA was made by the attending physician (and the patient was treated accordingly) even if EORTC/MSG criteria for probable or proven IPA
were not met.
M.-L. Luong et al. / Diagnostic Microbiology and Infectious Disease 68 (2010) 132–139
137
Table 4
Unadjusted and adjusted hazard ratios of 60-day mortality among patients with hematologic malignancies who underwent BAL to investigate respiratory disease
(n = 145)
Variable
BAL GM index value
b0.5
0.5–1.99
≥2
Age, per additional year
Male sex
HSCT
None
Autologous
Allogeneic
Hematologic malignancies
Othersa
Acute myelogenous leukemia
Neutropenia ≥10 daysb
Graft-versus-host disease (acute or chronic)
Steroid use in past 2 monthsc
T-cell immunosuppressives
Mold-active antifungal therapyd
Death/total (%)
13/106 (12.3)
2/18 (11.1)
10/21 (47.6)
NA
17/91 (18.7)
Unadjusted hazard ratio (95% CI)
Adjusted hazard ratio (95% CI)
1.00
0.90 (0.20–3.97)
4.68 (2.05–10.68)⁎⁎
0.99 (0.96–1.02)
1.31 (0.57–3.05)
1.00
0.82 (0.18–3.66)
2.66 (1.08–6.59)⁎
8/44 (18.2)
1/30 (3.3)
16/71 (22.5)
1.00
0.17 (0.02–1.39)
1.32 (0.56–3.08)
11/101 (10.9)
14/44 (31.8)
10/31 (32.3)
9/41 (22.0)
15/65 (23.1)
13/64 (20.3)
16/55 (29.1)
1.00
3.30 (1.50–7.27)⁎
2.53 (1.14–5.63)⁎
1.49 (0.66–3.38)
1.92 (0.86–4.28)
1.41 (0.64–3.08)
3.24 (1.43–7.33)⁎
2.49 (1.08–5.75)⁎
1.25 (0.52–2.98)
2.64 (1.13–6.16)⁎
NA = not applicable.
a
Acute lymphoblastic leukemia, chronic lymphocytic leukemia, Hodgkin's lymphoma, non-Hodgkin's lymphoma, multiple myeloma, and aplastic anemia.
b
Neutrophils count b0.5 × 109 neutrophils/L.
c
Prednisone, 0.3 mg/kg a day, equivalent for N3 weeks.
d
Voriconazole, itraconazole, caspofungin, amphotericin B, and liposomal amphotericin B, within 2 days prior to bronchoscopy.
⁎ P b 0.05.
⁎⁎ P b 0.001.
and lobar consolidation (Buckingham and Hansell, 2003).
Thus, it is possible that these patients with positive culture for
Aspergillus sp. truly had IPA, despite presenting atypical
radiologic findings. While recent modifications in the EORTC/
MSG definitions were made in an attempt to increase sensitivity
for the diagnosis of IPA (De Pauw et al., 2008), these expertderived definitions may not be able to capture all cases of IPA.
Given this limitation, the specificity of BAL GM in our study
may be underestimated. Nevertheless, strict application of the
EORTC/MSG definitions was used to provide the most
conservative estimate of the performance characteristics of
this test.
There has been much controversy regarding the optimal
cutoff value for positivity of the Platelia GM EIA assay
(Herbrecht et al., 2002; Maertens et al., 2007; Marr et al.,
2004). Although the recommended cutoff value for serum
GM has been established at 0.5, the optimal cutoff value for
BAL GM has not yet been determined. Based on ROC
analysis, increasing the cutoff value in our study from 0.5 to
3.0 would improve the specificity. Given the increased
mortality risk associated with a BAL GM index greater than
2.0 and the marginal difference in performance between a
cutoff value of 2.0 and 3.0, we believe it is more appropriate
to increase the cutoff value from 0.5 to 2.0. This would
improve specificity from 78% to 93% while maintaining
100% sensitivity, consistent with previous studies (Clancy
et al., 2007; Husain et al., 2007; Nguyen et al., 2007).
In clinical practice, empiric treatment often reflects
physicians' suspicion of a specific disease and may serve as
a surrogate marker for that disease. In our study, 65 BAL
samples were obtained from patients receiving mold-active
antifungal therapy initiated by their treating physicians
because of high degree of clinical suspicion for IPA prior to
bronchoscopy. The strong correlation between mold-active
antifungal therapy and BAL GM positivity in our study
suggests that early clinical suspicion of IPA can be accurate
and predictive. In addition, even after adjusting for antifungal
therapy initiated for suspicion of IPA, a BAL GM N2.0 was
associated with poorer outcome, further supporting the added
value of this test. Although factors other than the ones
included in our regression model may confound this
association, BAL GM N2.0 carries an important prognostic
value, identifying patients at higher risk of mortality.
Certain limitations must be considered in the interpretation of our results. First, the exclusion of patients who did not
have thoracic CT scan may be a source of selection bias.
Second, clinician-based decision for bronchoscopy and
timing of bronchoscopy relative to aplasia onset are potential
sources of selection and observation biases. The variable
amount of collected BAL fluid may also have affected
antigen concentration. Standardizing BAL protocols would
circumvent this problem; however, this is not always
clinically feasible. Another alternative would be to normalize
BAL GM levels to a lung fluid analyte such as urea. This
approach has been used to standardize BAL cytokine
concentrations (Rennard et al., 1986).
In conclusion, in patients with hematologic malignancies,
the GM assay in BAL is a highly sensitive tool to screen for
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M.-L. Luong et al. / Diagnostic Microbiology and Infectious Disease 68 (2010) 132–139
suspected IPA. However, using the serum cutoff level of an
index ≥0.5 as the threshold of positivity carries a high rate of
false-positive results. Raising the cutoff level of positivity
from 0.5 to 2.0 improves the specificity without decreasing
sensitivity. This improves the clinical utility of the BAL GM
assay and provides an important tool in the diagnosis of this
challenging disease.
Acknowledgments
The authors thank the following laboratory technicians
who performed the GM assay: Danielle Dumulong, Mireille
Lavigne, Nathalie Bruneau, Fabienne Bastien, and Murielle
Crimo. We also want to acknowledge Sylvie Bélanger for
her chart review activities.
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