Previously, the nitroblue tetrazolium (NBT) test was the recognized diagnostic test for CGD. Relying on light microscopy, the NBT test relies on a subjective analysis of phagocyte nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity.1
The dihydrorhodamine (DHR) test is the most common test for identifying CGD
While some physicians still use the NBT test, it has been largely replaced by the flow cytometric DHR test.1
The DHR test has user-friendly steps and provides standardized and quantifiable results alongside enhanced sensitivity.1
The DHR test produces fewer false-negative results than the NBT test and is known for its2,3:
May distinguish between X-linked and autosomal
recessive forms of CGD
Ability to evaluate X-linked carriers possibly at risk
for infections
High sensitivity that can detect low levels of
NADPH activity
Ability to quantitatively assess residual superoxide
production
Testing may help identify patients before a serious infection occurs.
See how timely management of CGD can help
The DHR test has largely replaced the NBT test to diagnose CGD.1
If you suspect CGD,
get a DHR Collection Kit at no cost to
confirm a diagnosis
What to look for when reading DHR histograms: Examples of pre- and post-activation DHR histograms
INDIVIDUAL WITHOUT CGD
The histograms show the difference in neutrophil NADPH oxidase activity in both an unstimulated sample and a sample that has been stimulated with PMA. There is a strong shift on the x-axis after PMA stimulation, indicating normal, robust neutrophil NADPH oxidase activity.
Unstimulated sample
After PMA stimulation*
PATIENT WITH X-LINKED CGD
The histogram for the stimulated sample shows almost no shift along the x-axis, indicating an absence of neutrophil oxidative burst due to defective NADPH oxidase function.
Unstimulated sample
After PMA stimulation*
X-LINKED FEMALE CGD CARRIER†
The stimulated sample shows 2 populations of cells. In one population, there is minimal shift along the x-axis because of the absence of NADPH oxidase activity. The other population does have NADPH oxidase activity, as indicated by the shift along the x-axis to the right. This is a sample only and is not inclusive of the various possible results for X-linked carriers.
Unstimulated sample
After PMA stimulation*
PATIENT WITH AUTOSOMAL RECESSIVE CGD
The stimulated sample shows a low degree of neutrophil NADPH oxidase activity, as demonstrated by a shift to the right along the x-axis that is much less dramatic than in histograms of patients with X-linked CGD along the x-axis. Both males and females can present with autosomal recessive CGD.
Unstimulated sample
After PMA stimulation*
X-linked carriers, who are often diagnosed after a diagnosis of a relative with X-linked CGD, must be identified early to prevent disease progression and poor outcomes.4,5
An X-linked carrier with a DHR level under 20% is at increased risk of infection.6‡
An X-linked carrier with a DHR level under 10% is highly associated with infection.6‡
These values are representations of possible DHR outcomes. Because of heterogeneity in disease severity and genotype, outcomes will vary. Laboratory results typically include percentage (%) of residual oxidative burst values.
See a patient case demonstrating how DHR values may change over time
Review tips for proper use of the DHR Collection Kit
MFI, mean fluorescence intensity; PMA, phorbol myristate acetate.
*PMA is an activator used to stimulate neutrophil NADPH oxidase activity.
†Usually a female with a healthy and a mutated allele for gp91phox.
Adapted from Leiding JW, et al (2013)3 and Jirapongsananuruk O, et al (2003).7
‡Symptomatic autoimmunity does not correlate with DHR levels, but is associated with the carrier state.6