Duffy-Null Phenotype-Associated Neutropenia is the Most Common Etiology for Leukopenia/Neutropenia Referrals to a Tertiary Children's Hospital

Duffy-null phenotype-associated neutropenia was present in 77.7% of leukopenia/neutropenia referrals to our center in Detroit with a high prevalence in Yemeni (96.6%), African American (91%), and non-Yemeni Middle Eastern (52.9%) patients. Greater availability of Duffy typing in patients with neutropenia but without recurrent/frequent/serious infections may lessen the need for additional consultations and investigations.

Diagnosis and management of isolated neutropenia: A survey of pediatric hematologist oncologists

BACKGROUND

Isolated neutropenia is a common referral to pediatric hematology oncology (PHO) physicians. There are no established consensus guidelines in the diagnosis and management of patients with isolated, asymptomatic, and incidentally discovered neutropenia.

METHODS

A survey was distributed to PHO physicians on the American Society of Pediatric Hematology Oncology member discussion page to determine the common diagnostic and management decisions regarding patients with isolated neutropenia and to explore beliefs regarding the term "benign ethnic neutropenia."

RESULTS

One hundred twenty-six PHO attending physicians completed the survey. The most common tests reportedly ordered for this patient population included complete blood cell count (CBC) (98%), peripheral smear (75%), antineutrophil antibody testing (29%), and immunoglobulins (24%). Providers were more likely to order an antineutrophil antibody in toddlers (p = .0085), and antinuclear antibody (ANA) panels in adolescents (p < .001). Half of providers do not request additional CBCs prior to their initial consultation, and most suggest referring patients with mild neutropenia after confirming a declining absolute neutrophil count (ANC) (51%). The three most important factors influencing ongoing follow-up included: history of recurrent/severe infections (98%), family history of blood disorders (98%), and more severe/progressively worsening neutropenia (97%). Seventy percent of respondents have diagnosed patients with "benign ethnic neutropenia," and 75% support replacement of the term to "typical neutrophil count with Fy(a-/b-) status," if confirmed with red cell phenotyping.

CONCLUSION

We identified practice patterns of PHO physicians for the diagnosis and management of patients referred for asymptomatic and isolated neutropenia. These data provide the framework to conduct cost-effectiveness studies.

Hematologic safety of palbociclib in combination with endocrine therapy in patients with benign ethnic neutropenia and advanced breast cancer

BACKGROUND

Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors, including palbociclib, are approved to treat hormone receptor (HR)-positive/human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer (ABC) and are associated with hematologic toxicity. African American women, who are underrepresented in CDK4/6 inhibitor clinical trials, may experience worse neutropenia because of benign ethnic neutropenia. The authors specifically investigated the hematologic safety of palbociclib in African American women with HR-positive/HER2-negative ABC.

METHODS

PALINA was a single-arm, open-label, investigator-initiated study of palbociclib (125 mg daily; 21 days on and 7 days off) plus endocrine therapy (ET) in African American women who had HR-positive/HER2-negative ABC and a baseline absolute neutrophil count ≥1000/mm³ (ClinicalTrials.gov identifier NCT02692755). The primary outcome was the proportion of patients who completed 12 months of therapy without experiencing febrile neutropenia or treatment discontinuation because of neutropenia. Single nucleotide polymorphism analysis was used to assess Duffy polymorphism status.

RESULTS

Thirty-five patients received ≥1 dose of palbociclib plus ET; 19 had a Duffy null polymorphism (cytosine/cytosine). There were no reports of febrile neutropenia or permanent study discontinuation because of neutropenia. Significantly more patients with the Duffy null versus the wild-type variant had grade 3 and 4 neutropenia (72.2% vs 23.1%; P = .029) and required a palbociclib dose reduction (55.6% vs 7.7%; P = .008). Patients with the Duffy null versus the wild-type variant had lower overall relative dose intensity (mean ± SD, 81.89% ± 15.87 and 95.67% ± 5.89, respectively; P = .0026) and a lower clinical benefit rate (66.7% and 84.6%, respectively).

CONCLUSIONS

These findings suggest that palbociclib is well tolerated in African American women with HR-positive/HER2-negative ABC. Duffy null status may affect the incidence of grade 3 neutropenia, dose intensity, and possibly clinical benefit.

Isolated Neutropenia/Benign Ethnic Neutropenia: A Common Clinical and Laboratory Finding in Southern and Western Saudi Arabia

OBJECTIVE

Isolated mild neutropenia is a common clinical problem in some ethnicities including Arabs and Middle Eastern population. The current study aims to authenticate the prevalence of isolated neutropenia in Southern and Southwestern Saudi Arabia, explore the effect of altitude or regional differences and to suggest a new reference range for neutrophil count.

METHODS

In this retrospective cross-sectional study, laboratory results of a commercial laboratory were screened over a period of 5 years (2016-2020) in seven different cities of different altitudes in South and southwestern Saudi Arabia. Participants' laboratory investigations were reviewed and excluded for any abnormal complete blood count, renal profile, liver profile, lipid profile, thyroid function test, fasting blood glucose, or HbA1c findings. Descriptive analysis and 95th percentile range were calculated using standard statistical methods.

RESULTS

A total of 91,880 complete blood count results were included in the final analysis. Isolated neutropenia was common laboratory finding, with a prevalence ranging from 11% to 23%. The 2.5th percentile of the neutrophil count was lower than currently utilized 1.5×109/L in all studied seven cities.

CONCLUSION

Mild to moderate neutropenia is common in Southern and Southwestern Saudi Arabia. Benign ethnic neutropenia (BEN) likely explains this high prevalence. Since BEN has no clinical significance, the reference range for normal neutrophil counts needs to be adjusted to reflect the effect of BEN.

Evaluation of the Safety of Clozapine Use in Patients With Benign Neutropenia

OBJECTIVE

To determine if clozapine can be safely utilized in psychiatric patients with benign neutropenia.

METHODS

A single-center, retrospective chart review study of records from 2001 to 2014 was conducted in an inpatient psychiatric hospital. Patients included had benign neutropenia prior to receiving clozapine and received clozapine using modified monitoring guidelines. All available laboratory values for absolute neutrophil count (ANC) before initiation and during treatment were evaluated. The primary endpoint was difference in ANC after initiation of clozapine from before clozapine.

RESULTS

A total of 26 patients were reviewed. The mean age at clozapine initiation was 34 years. The majority were African-American (73% [n = 19]), with more men than women (73% [n = 19] vs 27% [n = 7]). The mean lowest ANC value was not significantly different after clozapine initiation compared to before (1.5× 10³ cells/mm³ and 1.4 × 10³ cells/mm³, respectively; P = .22). The overall mean ANC was significantly higher after initiation than before (2.63 × 10³ cells/mm³ and 2.13 × 10³ cells/mm³, respectively; P < .001). There were no cases of severe neutropenia (ANC < 0.5 × 10³ cells/mm³), and no patient was discontinued for falling below modified guideline limits. There were fewer occurrences of mild neutropenia (ANC < 2.0 × 10³ cells/mm³) after clozapine initiation than before (16.0% and 31.4%, respectively; P < .001). There were also fewer occurrences of moderate neutropenia (ANC < 1.5 × 10³ cells/mm³), with 2.1% after clozapine and 13.3% before (P < .001).

CONCLUSIONS

Twenty-six patients with benign neutropenia were safely treated with clozapine. Pre-clozapine neutropenia did not predict increased risk for severe neutropenia with clozapine. Patients had significantly fewer episodes of mild and moderate neutropenia after receiving clozapine compared to before.

Identification and Clinical Characterization of Children With Benign Ethnic Neutropenia

Benign ethnic neutropenia (BEN) is an asymptomatic condition reported in adults of African and Middle Eastern descent. The clinical description in children is currently lacking. In our urban outpatient pediatric hematology clinic, the median neutrophil count of children with BEN was lower than previous reports in adults at 893×10 cells/L, but increased with older age. There was an equal male to female ratio and 24% of our BEN children reported ethnicities other than African or Middle Eastern. Children with BEN had a clinical course comparable with other healthy children including otherwise normal blood counts, except for mild anemia.

Clozapine underutilization and discontinuation in African Americans due to leucopenia

Clozapine use has been notably lower in African American patients than in Caucasians. It has been suggested that lower normal ranges for white blood cell (WBC) counts in African Americans, known as benign ethnic neutropenia, may account partially for the disparity. We examined the rates of leucopenia and agranulocytosis as reasons for discontinuation of clozapine in a sample of 1875 patients with schizophrenia treated in the State of Maryland. Between 1989 and 1999, 5.3% (31/588) of African Americans and 2.4% (31/1287) of Caucasians discontinued clozapine treatment due to leucopenia (chi square = 10.35, df = 1, P = 0.001). No African American patients developed agranulocytosis while 8 Caucasian patients (0.62%) developed this blood dyscrasia. Discontinuations due to leucopenia occurred throughout treatment. Discontinuations due to agranulocytosis occurred primarily in the first 18 weeks (7/8; 87.5% patients with agranulocytosis). It is likely that African Americans had clozapine discontinued unnecessarily due to benign ethnic neutropenia. We concur with recent recommendations to acknowledge differences in WBC values in African Americans and to modify prescribing guidelines or formally acknowledge benign ethnic leucopenia like in other countries in order to facilitate greater use of clozapine in these patients.