Chapter 18 Disorders of Phagocyte Function
Clinical Approach to Patients With Disorders of Phagocyte Function
Evaluation

Figure 18-1 STEPS IN THE RESPONSE OF CIRCULATION NEUTROPHILS TO INFECTION.
(Modified from Kyoto W, Coates TD: A practical approach to neutrophil disorders. Pediatr Clin North Am 49:929, 2002, with permission.)
Diagnosis of Chronic Granulomatous Disease
NBT Slide Test
• No NBT reduction (absence of cells with dark blue formazan deposits) in both X-linked and AR forms of CGD (see Fig. 18-3, B).
• Usually no reduction in 50% of cells and normal in 50% for X-linked carrier. The percent positive cells can vary if there is unequal X inactivation and may appear normal or like CGD with extreme lyonization (see Fig. 18-3, C).
• False-positive results can occur (i.e., apparent failure to reduce NBT supporting the diagnosis of CGD) if the neutrophils do not adhere to the slide. This happens with greasy slides or with some cases of LAD. Using PMA to stimulate the cells will avoid this.
DHR Flow Cytometry
• This approach has replaced the NBT slide test in many laboratories. It has the advantage of assessing large numbers of cells and can give quantitation of the amount of oxidant production.
• The change in fluorescence channel number with stimulation is the critical number and not the percent positive cells.
• X-linked CGD patients will not respond at all and show no increase in fluorescence with stimulation (see Fig. 18-3, F).
• X-linked carriers will show about 50% of the cells that respond with a normal increase in fluorescence, and the other half will have no response. Degrees of unequal X inactivation are much more accurately quantified by this assay (see Fig. 18-3, G).
• AR patients, particularly those with absent p47phox, have some response to stimulation and show a small increase in fluorescence (see Fig. 18-3, H). This level of oxidant production is usually not visible on the NBT test.