Laboratory Findings in Chronic Granulomatous Disease
The definitive laboratory finding in chronic granulomatous disease (CGD) is a defect in oxidative metabolism demonstrated by functional studies of neutrophil respiratory burst, most commonly assessed using the dihydrorhodamine (DHR) flow cytometry assay. 1
Key Laboratory Abnormalities
Neutrophil Count Patterns
Laboratory evaluation of CGD reveals variable neutrophil patterns that can initially mislead clinicians 1:
- Neutropenia (low neutrophil counts)
- Normal neutrophil numbers
- Marked neutrophilia (particularly in cellular adhesion defects)
This variability means you cannot rule out CGD based on neutrophil count alone—the functional defect is what matters.
Immunoglobulin Abnormalities
Hypergammaglobulinemia is a characteristic finding in CGD patients 2. This reflects chronic immune stimulation from recurrent infections and inflammatory processes. The elevated immunoglobulins are a red flag that should prompt consideration of phagocyte defects when combined with the appropriate clinical picture.
Other Common Laboratory Findings
Additional supportive laboratory abnormalities include 2:
- Anemia (often chronic disease-related)
- Leukocytosis (during active infections or inflammation)
Diagnostic Testing
Primary Diagnostic Test: DHR Flow Cytometry
The dihydrorhodamine (DHR) flow cytometry assay is the gold standard screening test 3, 4. This test:
- Measures hydrogen peroxide (H₂O₂) production by neutrophils
- Uses phorbol-myristate-acetate (PMA) or E. coli bacteria as stimuli
- Shows peak channel fluorescence >700 in normal patients (mean 840 ± 59)
- Demonstrates values clearly below normal range in CGD patients 4
The DHR assay is superior to older methods because it's quick, cost-effective, and at least as sensitive as chemiluminescence testing 3, 4.
Historical Test: Nitroblue Tetrazolium (NBT) Test
The NBT reduction test shows 0% reduction in most CGD patients (14 of 18 patients in one series) 2. While historically important, this has largely been replaced by DHR flow cytometry in modern practice.
Confirmatory Testing
After establishing defective oxidative burst 4:
- Cytochrome b558 expression can be measured using monoclonal antibody 7D5 (normal range: peak channel fluorescence 485-680)
- Genetic testing to identify specific mutations in CYBB, CYBA, NCF1, NCF2, or CYBC1 5, 6
Special Diagnostic Considerations
Variant Forms of CGD
NCF4/p40phox deficiency presents as a mild, atypical form without invasive infections and requires serum-opsonized E. coli as stimulus in the DHR assay for diagnosis 5. Standard PMA stimulation may miss this variant.
CYBC1/Eros deficiency is a rare form showing loss of respiratory burst AND absent gp91phox expression in phagocytes 5.
Female Carriers
X-linked female carriers require testing as they may present with partial or full CGD picture depending on lyonization patterns 5, 3. The DHR assay can identify carrier status by showing mixed populations of normal and abnormal neutrophils.
Clinical Correlation
The laboratory findings must be interpreted alongside the clinical picture of 3, 7:
- Recurrent infections with specific pathogens: S. aureus, Aspergillus spp., Burkholderia cepacia, Serratia marcescens, Nocardia spp.
- Granuloma formation (gastrointestinal/genitourinary systems)
- Inflammatory complications including colitis
Critical pitfall: Normal neutrophil counts do not exclude CGD—always proceed to functional testing (DHR assay) when clinical suspicion exists based on infection patterns and inflammatory manifestations 1.