A low neutrophil count does not always mean your immune system is impaired. Some healthy people have a persistently lower absolute neutrophil count (ANC) because they have the Duffy-null blood-cell phenotype. This is often called Duffy-null-associated neutrophil count (DANC), or ACKR1/DARC-associated neutropenia. The key is to distinguish a stable baseline from a new or unexplained change.
What A Low Neutrophil Count Means
Neutrophils are white blood cells that help defend against infection. ANC measures how many are circulating in your blood. Many laboratories flag an ANC below 1.5 × 109/L (1,500 cells/µL), but a flag is a prompt to interpret the result, not a diagnosis by itself. The person’s usual count, other blood-test results, symptoms and clinical history matter too.
With DANC, the count in the bloodstream tends to be lower, but clinical reviews report no increased infection risk simply because a person has this baseline. That does not mean every low result is harmless: infections, medicines and other conditions can also lower neutrophils.
Why Duffy-Null Status Matters
Duffy-null status is associated with a variant in the ACKR1 gene. It results in the absence of Duffy antigens on red blood cells and is linked to fewer circulating neutrophils. The variant is more common among people with African and some Middle Eastern ancestry, but people of any genetic ancestry can have it. Race, appearance or family origin cannot establish an individual’s status.
In a study by Minoo Bagheri and colleagues at Vanderbilt University Medical Center in Nashville, researchers examined blood counts from 3,739 participants who identified as Black and had no recorded blood cancer. The data came from health-maintenance examinations in Vanderbilt’s BioVU DNA biobank. Participants with the Duffy-null genotype had a lower median first ANC than those with other genotypes: 3,270 versus 4,830 cells/µL. Among adults with the genotype, 17.3% had at least one recorded ANC below 1,500 cells/µL and 5.5% below 1,000 cells/µL. These findings show why a standard cutoff can flag some people with DANC; the study does not mean every low count in a person of African ancestry is DANC.
How Clinicians Tell DANC From Acquired Neutropenia
Clinicians look at the pattern, not just one result. They may compare earlier blood counts, repeat the test, ask about recent infections and medicines, and check whether other blood-cell types are also low. Depending on your history and examination, they may consider tests such as a blood film, vitamin B12 and folate levels, or tests for particular infections or autoimmune conditions.
A stable, isolated low ANC over time, with no concerning symptoms or other blood-count abnormalities, can fit DANC. By contrast, a recent fall from your usual level, a downward trend, or low red cells or platelets as well as neutrophils calls for a broader assessment. Viral infections and medicines are among the possible acquired causes; autoimmune conditions, nutritional deficiencies and bone-marrow disorders are other possibilities.
Duffy status can be checked with red-cell antigen testing or genetic testing. If it is relevant, ask your clinician whether testing is appropriate rather than relying on ancestry as a shortcut. Confirming Duffy-null status can help put a persistent count in context, but it does not rule out a separate cause of a new change.
When Further Testing Is Warranted
Further evaluation is more important when a low ANC is new, worsening or accompanied by recurrent infections, mouth ulcers, unusual bruising, other abnormal blood counts, or findings such as enlarged lymph nodes or spleen. A very low count also deserves prompt clinical review. Local guidance differs on repeat-testing intervals and referral thresholds, so your clinician will interpret the result alongside your symptoms and medical history.
If you feel acutely unwell or have a fever and have been told your neutrophil count is very low, seek urgent medical advice. For a stable, long-standing result, bring previous blood tests and a current medicines list to your appointment. That history can help your clinician decide whether monitoring, Duffy testing or a wider investigation makes sense. This guide cannot determine the cause of an individual result; discuss persistent or concerning findings with a healthcare professional.
