Historically, the nitroblue tetrazolium (NBT) test has been the recognized diagnostic test for chronic granulomatous disease (CGD). Relying on light microscopy, the NBT test provides only a qualitative determination of phagocyte nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity.
The dihydrorhodamine (DHR) test produces fewer false-negative results than the NBT test and is known for its1,2:
Relative ease of use
Ability to distinguish between X-linked (gp91phox) and autosomal
recessive forms of CGD
Ability to detect carrier status
High sensitivity that can detect low levels of NADPH activity
Ability to quantitatively assess residual superoxide production
If you suspect CGD,
get a DHR Collection Kit at no cost to
confirm a diagnosis
Examples of pre- and
postactivation DHR histograms
What to look for when reading DHR histograms
INDIVIDUAL WITHOUT CGD
The histograms below 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.
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. Both males and females can present with autosomal recessive CGD.
Unstimulated sample
After PMA stimulation*
These values are representations of possible DHR outcomes. Because of heterogeneity in disease severity and genotype, outcomes will vary. Lab results typically include percentage (%) of residual oxidative burst values.
Abbreviations: 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).4
Importance of family testing
Because CGD is an inherited disorder, families of patients with CGD may benefit from DHR testing. Testing can help distinguish CGD subtype and identify carrier status.
An X-linked carrier mother has a 50% chance of having a carrier daughter or an affected son.2 With autosomal recessive CGD, both parents are carriers. Each child has a 75% chance of being affected or a carrier.2
Carriers may benefit from genetic counseling prior to starting a family. While CGD carriers themselves are usually not affected, they can exhibit CGD-like symptoms such as5-7:
- Dermatitis
- Stomatitis
- Discoid lupus-like disease
- Photosensitive rashes