Transcript Daily cost of therapy with lipid preparations of AmB

Galactomannan testing: lessons
from the last decade
Claudio Viscoli
Professor of Infectious Disease, University of
Genova
Chief, Division of Infectious Disease, San
Martino University Hospital, Genova, Italy
Galactomannan antigen detection
Platelia Aspergillus – ELISA (Bio-Rad)
Galactomannan antigen
Platelia Aspergillus (Bio-Rad)
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Sensitivity highly variable (29-100%)

Specificity generally better (81-98%)

FDA approved
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Important tool in the diagnosis of aspergillosis (EORTC-MSG
definitions of IA (Ascioglu 2002)
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May be positive before the occurrence of clinical and
radiological signs/symptoms

Two main strategies of use:

Serial collection of samples (2 or 3 times/week) in high risk
patients

Intensive testing in symptomatic patients (unexplained persistent
fever unresponsive to broad spectrum antibiotics )
Galactomannan antigen
Platelia Aspergillus (Bio-Rad)
Controversies
 Different cut-off used: 0.5, 0.7, 1, 1.5
Drawbacks
 False positive and false negative results
 Too low sensitivity according to some authors
(Pinel 2003, Allan 2005)
Galactomannan antigen
CUT-OFF FOR POSITIVITY
Test result as GM index = sample OD/cut-off OD (1 ng/ml )
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Index > 1.5 in 2 consecutive samples
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Index > 1
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Index > 0.7 (sensitivity+24%;specificity-5.5% compared
with BIO-RAD cut-off) (Herbrecht 2002)

Index > 0,5 (sensitivity 5083%,specificity 10073,7%
compared with BIO-RAD cut-off (Marr 2004)
(BIO-RAD)
(Verweij 1998; Maertens 2001; Sulahian 2001; Ascioglu 2002)
Static cut-off
Single test Index > 0.7
(Maertens 2004)
Dynamic cut-off
Two consecutive test Index > 0.5
Galactomannan antigen
From 1998 to July 2009: 24.093 Galactomannan determinations with Platelia Aspergillus
(ELISA) (mean: 2007 determinations/year; min 332, max 4402)
Galactomannana determinations
5000
4500
4000
3500
3000
2500
2000
1500
1000
500
0
98
19
99
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00
20
01
20
02
20
03
20
04
20
05
20
06
20
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20
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20
9
00
2
ly
Ju
year
We perform GM test in serum, BAL, sputum, CSF, pleural fluid, tracheal aspirate fluid and synovial fluid.
Why we have false positive
results?
Aspergillus galactomannan
False positive results
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Transient antigenemia (non invasive infections?)
Cross reactivity with exoantigens (bacteria-fungi)
Induction by cyclophosphamide
Premature infants (83%)
Cotton swabs
(Hashiguchi et al. 1994)
(Siemann et al. 1998)
(Dalle et al. 2002)
Absorption of galactomannan through a damaged
intestinal mucosa (Letscher-Bru et al. 1998)
 During caspofungin therapy (Petraitiene et al. 2002)
 Galactomannan in antibiotics (Ansorg et al. 1997; Viscoli et
2003)
al
Fungal organism likely testing positive with the
Platelia test
Routine use of the GM test at the
BMT Unit in Genova from Jan. 1999
to May 2003
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Total number of patients
Total number of serum samples
Median samples per patient
Median samples per month
Median positivity rate per month
• Jan. 1999 - Jan. 2003
• Feb. 2003 - May 2003
420
4702
7 (1-64)
85 (35-146)
9% (0-18)
24% (20-44)
mag-03
mar-03
gen-03
nov-02
set-02
lug-02
mag-02
mar-02
gen-02
nov-01
set-01
lug-01
mag-01
mar-01
gen-01
nov-00
set-00
lug-00
mag-00
mar-00
gen-00
nov-99
set-99
lug-99
mag-99
mar-99
gen-99
Monthly proportion of positive samples
60%
36% of patients and
28% of specimens were positive
50%
40%
30%
20%
10%
0%
Platelia Aspergillus Test results by administration
of Piperacillim-Tazobactam
Patient receiving
piperacillin-tazobactam
26%
Patient NOT receiving
piperacillin-tazobactam
Positive
74%
89%
Negative
Pipera-tazo YES= since at least 24 hrs
Viscoli et al ICAAC 2003; CID 2004
11%
p < 0,001
Platelia Aspergillus test
on piperacillin-tazobactam
 six batches of Tazocin taken from
the hospital pharmacy were tested
 two 4.5 g. vials per batch
 diluted with 100 ml NaCl 0.9%
 five of six batches tested positive
 median GM index 4.7 (1.5-5.7)
Galactomannan antigen
FALSE POSITIVE IN PEDIATRIC PATIENTS
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False positive GM test in 83% of premature infants
(prolonged ICU and birth weight of 400-1320 g)
(Siemann 1998)
Passage of food-GM through damaged intestinal mucosa of BMT
children (Letscher-Bru 1998)
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Neonates milk formula, false positive GM test (Gangneux 2002)
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Bifidobacterium sp. lipoteichoic acid (bacteria that heavily colonize
neonatal gut) produces false positive GM test
(Mennink-Kersten
2004)
Clinical Microbiology and Infection, in press
Why we have false negative
results?
•
•
•
•
•
•
•
Low prevalence of the disease
Concomitant use of antifungals
Little angioinvasion (HSCT)
Presence of anti-aspergillus antibodies
Low fungal burden
Inappropriate cut-off
Inappropriate use
 Testing
 Sampling
 Storage
Pfeiffer et al., CID, 2006
Antifungal therapy
Yes
No
0,5
0,5
1
1
1,5
1,5
(Marr 2005)
Filtration and use of a larger volume of serum
Conventional method
Verwej 2005
Galactomannan in other body fluids
GM in CSF
(Klont RR, CID, 2004)
Cerebral aspergillosis 10%-20% of all acses of invasive aspergillosis
•Not validated
•Cut-off?
Aspergillus galactomannan antigen
detection in cerebral aspergillosis
GM index in CSF
Box-plot analysis of CSF GM in patients with or without cerebral
aspergillosis, demonstrating the specificity of the test when performed in
the CSF
Cerebral aspergillosis
(5 pts; 8 samples)
Control patients
(16 pts; 33 samples)
(Viscoli et al. 2001)
Galactomannan as a surrogate marker
of efficacy
Galactomannan levels in serum and
CSF samples
7
Elisa serum result
Index = 29,45
6
Elisa CSF result
5
Elisa positivity
threshold
4
3
Clinical sign of
aspergillosis
2
1
0
50
55
60
65
70
75
Days from BMT
80
85
90
95
100
(Machetti et al. 2000)
Thank you for your
attention
Pfeiffer et al., CID, 2006
Comparison of empirical and PCR-based
preemptive antifungal therapy in 408
allogeneic stem cell transplant recipients
• PCR screening twice weekly during stay in hospital and once weekly
after discharge until D100
• Antifungal therapy initiation
 PCR group: in PCR+ patients with signs of infection and in patients
with 2 consecutive PCR +
 Empirical treatment group: 5d of febrile neutropenia
PCR based
n = 196
Antifungal therapy
109 (56%)
Proven invasive aspergilosis
11
Empiric
n = 207
76 (37%)
16
(p<0.05)
• Reduction in early mortality (D30) in patients receiving PCR-based
therapy but no difference in mortality at D100 and D180
(Hebart et al. ASH 2004)