Duffy phenotyping and FY*B-67T/C genotyping as screening test for benign constitutional neutropenia

The highest Duffy (FYX) allele frequency ever reported for Scottish population: A cross-sectional study

Background and Aim

The Duffy (FY) blood group system has six known antigens among which the Fya and Fyb are known as major antigens. Fyx phenotype forms as a result of two point mutations in the FYB allele leading to instability of Duffy protein and so reduction of Duffy antigen expression in the cells. This study aimed to investigate the FYX allele frequency in the Scottish population.

Methods

The Duffy blood group system was serologically and molecularly investigated in 222 samples collected from donors of Aberdeen Regional Blood Transfusion Center (BTC). The haemagglutination and BeadChip microarray chemistry methods were used for phenotyping and genotyping. Confirmatory tests were also used to check the discrepant results.

Results

In this study, the frequency of Duffy blood group phenotypes including Fya+, Fya+b+, and Fyb+ were 17.57%, 42.79%, and 39.64%, respectively. Furthermore, the frequency of FYA/FYA, FYA/FYB, and FYB/FYB genotypes was estimated to be 14.41%, 45.95%, and 39.64%, respectively, using the Bioarray method. In the present study, based on Duffy DNA sequencing results, 12 samples (5.41%) had just one FYX allele.

Conclusion

The frequency of the FYX allele in this study was estimated to be 0.0270% which is more than the results reported so far.

Benign ethnic neutropenia: an analysis of prevalence, timing and identification accuracy in two large inner-city NHS hospitals

BACKGROUND

Benign ethnic neutropenia (BEN) is the most common cause of chronic neutropenia seen in individuals of African, Middle Eastern and West Indian descent. This phenotype is broadly defined by an absolute neutrophil counts (ANC) below 1.8 × 10⁹ cells/L in the absence of other causes, without an increased risk of infection. BEN has been implicated as a potential source of disparity in patients treated with clozapine, the antipsychotic of choice in treatment-resistant schizophrenia. Our main objective was to examine the current level of BEN recognition in a cohort of patients treated with clozapine and the potential impact of unidentified BEN on the initiation and maintenance of clozapine treatment.

METHODS

This was an observational, retrospective analysis of patients registered with clozapine haematological monitoring systems in two large mental health trusts, chosen because they serve an ethnically diverse population. The first objective was to establish certified BEN prevalence in current users of clozapine. The second objective was to explore the stage of treatment at which BEN was identified. The third objective was to evaluate the extent of unrecognised BEN in patients registered on the Central Non-Rechallenge Database (CNRD), a database for patients whose haematological parameters fall below set thresholds when receiving clozapine treatment, meaning they cannot ordinarily be prescribed clozapine again.

RESULTS

The study population comprised of 2020 patients on the clozapine register. 111 patients were monitored under BEN criteria. BEN was mostly identified after a below threshold haematological result or clozapine rechallenge (68%) compared to at clozapine initiation (32%). Eight of the 18 (42%) black patients registered on the CNRD were classified as BEN after assessment by a haematologist. Of these 8 patients, none would have met CNRD criteria again if monitored with BEN criteria at clozapine initiation.

CONCLUSIONS

Current evidence suggests that BEN remains an uncommonly recognised haematological phenotype. Improved timely identification of BEN will reduce unnecessary interruption or discontinuation of clozapine treatment. Our results suggest consideration should also be given to determining BEN status prior to initiating clozapine. Moreover, adoption of current FDA BEN monitoring criteria in the UK may further reduce clozapine discontinuation due to perceived neutropenia as drug toxicity, particularly in treatment-refractory schizophrenia patients.

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.