Race, Genotype, and Azathioprine Discontinuation : A Cohort Study

Lupus and other autoimmune diseases: Epidemiology in the population of African ancestry and diagnostic and management challenges in Africa

Autoimmune diseases are prevalent among people of African ancestry living outside Africa. However, the burden of autoimmune diseases in Africa is not well understood. This article provides a global overview of the current burden of autoimmune diseases in individuals of African descent. It also discusses the major factors contributing to autoimmune diseases in this population group, as well as the challenges involved in diagnosing and managing autoimmune diseases in Africa.

Using electronic health records for clinical pharmacology research: Challenges and considerations

Electronic health records (EHRs) contain a vast array of phenotypic data on large numbers of individuals, often collected over decades. Due to the wealth of information, EHR data have emerged as a powerful resource to make first discoveries and identify disparities in our healthcare system. While the number of EHR-based studies has exploded in recent years, most of these studies are directed at associations with disease rather than pharmacotherapeutic outcomes, such as drug response or adverse drug reactions. This is largely due to challenges specific to deriving drug-related phenotypes from the EHR. There is great potential for EHR-based discovery in clinical pharmacology research, and there is a critical need to address specific challenges related to accurate and reproducible derivation of drug-related phenotypes from the EHR. This review provides a detailed evaluation of challenges and considerations for deriving drug-related data from EHRs. We provide an examination of EHR-based computable phenotypes and discuss cutting-edge approaches to map medication information for clinical pharmacology research, including medication-based computable phenotypes and natural language processing. We also discuss additional considerations such as data structure, heterogeneity and missing data, rare phenotypes, and diversity within the EHR. By further understanding the complexities associated with conducting clinical pharmacology research using EHR-based data, investigators will be better equipped to design thoughtful studies with more reproducible results. Progress in utilizing EHRs for clinical pharmacology research should lead to significant advances in our ability to understand differential drug response and predict adverse drug reactions.

Prevalence of Duffy null and its impact on hydroxyurea in young children with sickle cell disease in the United States

Consistent with studies showing a high prevalence of the Duffy null phenotype among healthy Black Americans, this retrospective study found that Duffy null was present in >75% of a young and contemporary cohort of children with sickle cell disease (SCD) in the United States. Despite the potential for this phenotype to impact absolute neutrophil counts, hydroxyurea (HU) dosing, and outcomes, it was not associated with being prescribed a lower HU dose or having increased acute SCD visits early in the HU treatment course. Future studies are needed to confirm these findings in older children with SCD.

Clinical associations with a polygenic predisposition to benign lower white blood cell counts

Polygenic variation unrelated to disease contributes to interindividual variation in baseline white blood cell (WBC) counts, but its clinical significance is uncharacterized. We investigated the clinical consequences of a genetic predisposition toward lower WBC counts among 89,559 biobank participants from tertiary care centers using a polygenic score for WBC count (PGSWBC) comprising single nucleotide polymorphisms not associated with disease. A predisposition to lower WBC counts was associated with a decreased risk of identifying pathology on a bone marrow biopsy performed for a low WBC count (odds-ratio = 0.55 per standard deviation increase in PGSWBC [95%CI, 0.30-0.94], p = 0.04), an increased risk of leukopenia (a low WBC count) when treated with a chemotherapeutic (n = 1724, hazard ratio [HR] = 0.78 [0.69-0.88], p = 4.0 × 10-5) or immunosuppressant (n = 354, HR = 0.61 [0.38-0.99], p = 0.04). A predisposition to benign lower WBC counts was associated with an increased risk of discontinuing azathioprine treatment (n = 1,466, HR = 0.62 [0.44-0.87], p = 0.006). Collectively, these findings suggest that there are genetically predisposed individuals who are susceptible to escalations or alterations in clinical care that may be harmful or of little benefit.

Autoimmune inflammatory myopathy biomarkers

The autoimmune inflammatory myopathy disease spectrum, commonly known as myositis, is a group of systemic diseases that mainly affect the muscles, skin and lungs. Biomarker assessment helps in understanding disease mechanisms, allowing for the implementation of precise strategies in the classification, diagnosis, and management of these diseases. This review examines the pathogenic mechanisms and highlights current data on blood and tissue biomarkers of autoimmune inflammatory myopathies.

Eliminating Algorithmic Racial Bias in Clinical Decision Support Algorithms: Use Cases from the Veterans Health Administration

The Veterans Health Administration uses equity- and evidence-based principles to examine, correct, and eliminate use of potentially biased clinical equations and predictive models. We discuss the processes, successes, challenges, and next steps in four examples. We detail elimination of the race modifier for estimated kidney function and discuss steps to achieve more equitable pulmonary function testing measurement. We detail the use of equity lenses in two predictive clinical modeling tools: Stratification Tool for Opioid Risk Mitigation (STORM) and Care Assessment Need (CAN) predictive models. We conclude with consideration of ways to advance racial health equity in clinical decision support algorithms.

Clinical consequences of a polygenic predisposition to benign lower white blood cell counts: Consequences of benign WBC count genetics

Polygenic variation unrelated to disease contributes to interindividual variation in baseline white blood cell (WBC) counts, but its clinical significance is undefined. We investigated the clinical consequences of a genetic predisposition toward lower WBC counts among 89,559 biobank participants from tertiary care centers using a polygenic score for WBC count (PGSWBC) comprising single nucleotide polymorphisms not associated with disease. A predisposition to lower WBC counts was associated with a decreased risk of identifying pathology on a bone marrow biopsy performed for a low WBC count (odds-ratio=0.55 per standard deviation increase in PGSWBC [95%CI, 0.30 - 0.94], p=0.04), an increased risk of leukopenia (a low WBC count) when treated with a chemotherapeutic (n=1,724, hazard ratio [HR]=0.78 [0.69 - 0.88], p=4.0×10-5) or immunosuppressant (n=354, HR=0.61 [0.38 - 0.99], p=0.04). A predisposition to benign lower WBC counts was associated with an increased risk of discontinuing azathioprine treatment (n=1,466, HR=0.62 [0.44 - 0.87], p=0.006). Collectively, these findings suggest that a WBC count polygenic score identifies individuals who are susceptible to escalations or alterations in clinical care that may be harmful or of little benefit.

Development of Duffy Null-Specific Absolute Neutrophil Count Reference Ranges

This study establishes a Duffy null phenotype–specific absolute neutrophil count reference range to optimize care and improve health equity.

Prospects for targeting ACKR1 in cancer and other diseases

The chemokine network is comprised of a family of signal proteins that encode messages for cells displaying chemokine G-protein coupled receptors (GPCRs). The diversity of effects on cellular functions, particularly directed migration of different cell types to sites of inflammation, is enabled by different combinations of chemokines activating signal transduction cascades on cells displaying a combination of receptors. These signals can contribute to autoimmune disease or be hijacked in cancer to stimulate cancer progression and metastatic migration. Thus far, three chemokine receptor-targeting drugs have been approved for clinical use: Maraviroc for HIV, Plerixafor for hematopoietic stem cell mobilization, and Mogalizumab for cutaneous T-cell lymphoma. Numerous compounds have been developed to inhibit specific chemokine GPCRs, but the complexity of the chemokine network has precluded more widespread clinical implementation, particularly as anti-neoplastic and anti-metastatic agents. Drugs that block a single signaling axis may be rendered ineffective or cause adverse reactions because each chemokine and receptor often have multiple context-specific functions. The chemokine network is tightly regulated at multiple levels, including by atypical chemokine receptors (ACKRs) that control chemokine gradients independently of G-proteins. ACKRs have numerous functions linked to chemokine immobilization, movement through and within cells, and recruitment of alternate effectors like β-arrestins. Atypical chemokine receptor 1 (ACKR1), previously known as the Duffy antigen receptor for chemokines (DARC), is a key regulator that binds chemokines involved in inflammatory responses and cancer proliferation, angiogenesis, and metastasis. Understanding more about ACKR1 in different diseases and populations may contribute to the development of therapeutic strategies targeting the chemokine network.

Leveraging our common African origins to understand human evolution and health

In the March 2023 issue of Cell, Fan et al.¹ report whole-genome sequencing across 12 indigenous African populations and analyze local adaptation and evolutionary history. Here, Wonkam and Adeyemo highlight their findings and how this contributes to African and global genomic research.

Association Between Genetically Predicted Expression of TPMT and Azathioprine Adverse Events

Polymorphisms thiopurine-S-methyltransferase (TPMT) and nudix hydrolase 15 (NUDT15) can increase the risk of azathioprine myelotoxicity, but little is known about other genetic factors that increase risk for azathioprine-associated side effects. PrediXcan is a gene-based association method that estimates the expression of individuals' genes and examines their correlation to specified phenotypes. As proof of concept for using PrediXcan as a tool to define the association between genetic factors and azathioprine side effects, we aimed to determine whether the genetically predicted expression of TPMT or NUDT15 was associated with leukopenia or other known side effects. In a retrospective cohort of 1364 new users of azathioprine with EHR-reported White race, we used PrediXcan to impute expression in liver tissue, tested its association with pre-specified phecodes representing known side effects (e.g., skin cancer), and completed chart review to confirm cases. Among confirmed cases, patients in the lowest tertile (i.e., lowest predicted) of TPMT expression had significantly higher odds of developing leukopenia (OR=3.30, 95%CI: 1.07-10.20, p=0.04) versus those in the highest tertile; no other side effects were significant. The results suggest that this methodology could be deployed on a larger scale to uncover associations between genetic factors and drug side effects for more personalized care.

Ancestry, ACKR1 and leucopenia in patients with systemic lupus erythematosus

OBJECTIVE

SLE is more prevalent in populations of African (AA) than European ancestry (EA) and leucopenia is common. A homozygous variant in ACKR1 (rs2814778-CC) is associated with lower white cell counts; the variant is common in AA but not EA populations. We hypothesised that in SLE: (1) leucopenia is more frequent in patients of AA than EA, and (2) the ACKR1-CC genotype accounts for the higher frequency of leucopenia in AA patients.

METHODS

We performed a retrospective cohort study in patients with SLE at a tertiary care system. Ancestry was defined by genetic principal components. We compared the rate of leucopenia, thrombocytopenia and anaemia between (a) EA and AA patients, and (b) ACKR1-CT/TT and CC genotype in AA patients.

RESULTS

The cohort included 574 patients of EA and 190 of AA; ACKR1-CC genotype was common in AA (70%) but not EA (0%) patients. Rates of leucopenia for ancestry and genotype were AA 60.0% vs EA 36.8 % (p=1.9E-08); CC 67.7% vs CT/TT 42.1% (p=9.8E-04). The rate of leucopenia did not differ by ancestry comparing EA patients versus AA with CT/TT genotype (p=0.59). Thrombocytopenia (22.2% vs 13.2%, p=0.004) and anaemia (88.4% vs 66.2%, p=3.7E-09) were more frequent in AA patients but were not associated with ACKR1 genotype (p=0.82 and p=0.84, respectively).

CONCLUSIONS

SLE of AA had higher rates of anaemia, leucopenia, and thrombocytopenia than those of EA; only the difference in leucopenia was explained by ACKR1-CC genotype. This genotype could affect clinical practice.

Absolute neutrophil count by Duffy status among healthy Black and African American adults

Many people of African ancestry have lower absolute neutrophil counts (ANCs) without increased risk for infection. This is associated with the Duffy-null phenotype (nonexpression of the Duffy antigen on red blood cells), which is commonly found in those of African descent. Currently, there are no studies that compare the ANC of individuals with Duffy-null phenotype to those with Duffy non-null phenotypes within a self-identified Black population. The aim of this study was to assess the impact of Duffy status on ANCs based on complete blood counts with differential and Duffy testing in a healthy population of self-identified Black individuals at a single primary care center. This study found that 66.7% (80 of 120) of Black individuals have the Duffy-null phenotype and that there is a significant difference in ANCs between Duffy-null and Duffy non-null individuals (median, 2820 cells per μL vs 5005 cells per μL; P < .001). Additionally, 19 of 80 (23.8%) Duffy-null individuals had an ANC of <2000 cells per μL compared with no (0) Duffy non-null individuals. The Duffy-null phenotype is clinically insignificant; however, inappropriate reference ranges can propagate systemic racism. Therefore, we advocate for the development of Duffy-null-specific ANC reference ranges as well as replacing the term benign ethnic neutropenia with Duffy-nullassociated neutrophil count.