Diverse clinical features and diagnostic delay in monogenic inborn errors of immunity: A call for access to genetic testing

Diagnostic disparities in inborn errors of immunity: From clinical suspicion to diagnosis

Background

Emerging evidence suggests that inborn errors of immunity (IEI) are underdiagnosed among underserved populations. However, there remains a lack of national studies evaluating diagnostic disparities in IEI.

Objective

We examined disparities in the timely IEI diagnosis and related health outcomes.

Methods

A retrospective analysis was performed of a US national claims database (years 2007 to 2021). Participants included patients diagnosed with an "unspecified immune deficiency" (uID) and presented with IEI-related symptoms, who later received an IEI diagnosis (n = 1429). We quantified the diagnostic interval from clinical suspicion (uID) to IEI diagnosis and examined its association with sociodemographic factors and related health outcomes.

Results

The median (interquartile range) diagnostic interval was 369 (126-808) days. Diagnostic interval was 14% longer among patients residing in predominantly non-White neighborhoods, compared with those in predominantly White neighborhoods (P = .04), despite having more severe IEI-related symptoms at uID diagnosis and significantly more health care encounters for pneumonia (incidence rate ratio, 2.24; 95% confidence interval, 1.40-3.70) and sepsis (incidence rate ratio, 2.15; 95% confidence interval, 1.21-3.99) in the year after uID diagnosis. Residence in neighborhoods with greater deprivation was also associated with more severe IEI-related symptoms and greater health care utilization in the year after uID diagnosis. Older age was associated with longer diagnostic interval (P < .001). Longer diagnostic interval was associated with a longer interval to receiving IgR therapy (hazard ratio, 0.64; 95% confidence interval, 0.49-0.83).

Conclusion

We observed significant racial and socioeconomic disparities in the timeliness of IEI diagnosis and IEI-related outcomes. Further studies are needed to address the underlying factors contributing to diagnostic inequity.

Disparities in Genetic Testing for Inborn Errors of Immunity

BACKGROUND

Inequities in genetic testing have been documented in a range of diseases, and no-charge genetic testing programs have been proposed as a means to enhance access. However, no studies have examined disparities in genetic testing for inborn errors of immunity (IEI) and the impact of no-charge programs on testing equity.

OBJECTIVE

To examine socioeconomic, geographic, and racial disparities in the uptake of genetic testing for IEI in the United States and the impact of a no-charge sponsored program on testing equity.

METHODS

This was a retrospective cohort analysis of (1) a national claims database capturing individuals with IEI (n = 18,603), and (2) data from a clinical genetic testing laboratory capturing patients with IEI participating in a no-charge sponsored program (n = 6,681) and a non-sponsored program (n = 29,579) for IEI genetic testing.

RESULTS

Among patients with IEI captured in the claims database, those residing in areas of greater deprivation (odds ratio [OR] = 0.95; 95% CI, 0.92-0.98), rural areas (OR = 0.82; 95% CI, 0.71-0.96), and non-White neighborhoods (OR = 0.89, 95% CI 0.81-0.98) were less likely to undergo genetic testing. Participants in the sponsored IEI genetic testing program lived in areas of greater deprivation compared with the non-sponsored program (median, 46 vs 42; P < .001). However, historically excluded racial groups were underrepresented in both the sponsored and non-sponsored programs relative to disease burden.

CONCLUSIONS

We found significant disparities in genetic testing for IEI. Although eliminating the financial barriers to testing reduced socioeconomic disparities in genetic testing for IEI, racial disparities persisted. Further research is needed to address barriers to testing among underserved populations.

Inborn errors of immunity (primary immunodeficiencies)

Primary immunodeficiencies (PID), now often referred to as inborn errors of immunity (IEI), are a large heterogeneous group of disorders that result from deficiencies in immune system development and/or function. IEIs can be broadly classified as disorders of adaptive immunity (e.g., combined or humoral immunodeficiencies) or of innate immunity (e.g., phagocyte and complement disorders). Although the clinical manifestations of IEIs are highly variable, traditionally many disorders involve an increased susceptibility to infection. Research in recent years has underscored how IEI can present with features other than infection such as: severe atopy, autoimmunity, autoinflammation, lymphoproliferation, and/or malignancy resulting from immune dysregulation. Early consultation with a clinical immunologist is essential, as timely diagnosis and treatment are imperative for preventing significant disease-associated morbidity and mortality. The treatment of IEIs is complex and generally requires both supportive and definitive strategies, including but not limited to, immunoglobulin replacement therapy, antibiotic prophylaxis, immune response modifiers, and hematopoietic stem cell transplantation. This article provides an overview of the major categories of IEIs and strategies for the appropriate diagnosis and management of these disorders.

"I am sick, but that's not all that I am": patient perspectives on psychological adaptation over time to inborn errors of immunity

Inborn errors of immunity (IEI) are rare heritable disorders of the immune system predisposing to atypical infections, autoimmunity, inflammation, and risk of malignancy. Adaptation is the process of incorporating stressful experiences into one's life; these experiences may include onset of illness, receiving a diagnosis, or suffering without a diagnosis. Poor adaptation is linked to adverse outcomes including psychiatric comorbidities and decreased well-being. Most people with chronic illnesses and rare diseases adapt to their condition with time, but little is known about how this happens. We seek to address this gap in knowledge by investigating features of successful adaptation to IEI over time to help providers facilitate this process among those who struggle. We interviewed 20 self-reportedly well-adapted adults with IEI about their experiences of adaptation. We identified three overarching themes. First, many participants grappled with shame and loss but ultimately integrated their illness into their lives through acceptance, gratitude, and self-compassion. Second, knowledge and choice contributed to participants' perceived control, but most participants were also forced to acknowledge the limits of that control when confronting unpredictable symptoms. Finally, social relationships could influence adaptation either positively or negatively. Notably, many participants found meaning in giving back to their communities, especially by educating others about their condition. Ultimately, participants showed that adaptation to life with IEI is complex and ongoing, requiring frequent recalibration to emerging challenges in new life stages. We provide recommendations to providers to help the results of this study shape their discussions with patients.

Monogenic Inborn Errors of Immunity with impaired IgG response to polysaccharide antigens but normal IgG levels and normal IgG response to protein antigens

In patients with severe and recurrent infections, minimal diagnostic workup to test for Inborn Errors of Immunity (IEI) includes a full blood count, IgG, IgA and IgM. Vaccine antibodies against tetanus toxoid are also frequently measured, whereas testing for anti-polysaccharide IgG antibodies and IgG subclasses is not routinely performed by primary care physicians. This basic approach may cause a significant delay in diagnosing monogenic IEI that can present with an impaired IgG response to polysaccharide antigens with or without IgG subclass deficiency at an early stage. Our article reviews genetically defined IEI, that may initially present with an impaired IgG response to polysaccharide antigens, but normal or only slightly decreased IgG levels and normal responses to protein or conjugate vaccine antigens. We summarize clinical, genetic, and immunological findings characteristic for these IEI. This review may help clinicians to identify patients that require extended immunologic and genetic evaluations despite unremarkable basic immunologic findings. We recommend the inclusion of anti-polysaccharide IgG antibodies as part of the initial routine work-up for possible IEI.

Natural language processing of clinical notes enables early inborn error of immunity risk ascertainment

Background

There are now approximately 450 discrete inborn errors of immunity (IEI) described; however, diagnostic rates remain suboptimal. Use of structured health record data has proven useful for patient detection but may be augmented by natural language processing (NLP). Here we present a machine learning model that can distinguish patients from controls significantly in advance of ultimate diagnosis date.

Objective

We sought to create an NLP machine learning algorithm that could identify IEI patients early during the disease course and shorten the diagnostic odyssey.

Methods

Our approach involved extracting a large corpus of IEI patient clinical-note text from a major referral center's electronic health record (EHR) system and a matched control corpus for comparison. We built text classifiers with simple machine learning methods and trained them on progressively longer time epochs before date of diagnosis.

Results

The top performing NLP algorithm effectively distinguished cases from controls robustly 36 months before ultimate clinical diagnosis (area under precision recall curve > 0.95). Corpus analysis demonstrated that statistically enriched, IEI-relevant terms were evident 24+ months before diagnosis, validating that clinical notes can provide a signal for early prediction of IEI.

Conclusion

Mining EHR notes with NLP holds promise for improving early IEI patient detection.

Diagnostic delay in monogenic disease: A scoping review

PURPOSE

Diagnostic delay in monogenic disease is reportedly common. We conducted a scoping review investigating variability in study design, results, and conclusions.

METHODS

We searched the academic literature on January 17, 2023, for original peer reviewed journals and conference articles that quantified diagnostic delay in monogenic disease. We abstracted the reported diagnostic delay, relevant study design features, and definitions.

RESULTS

Our search identified 259 articles quantifying diagnostic delay in 111 distinct monogenetic diseases. Median reported diagnostic delay for all studies collectively in monogenetic diseases was 5.0 years (IQR 2-10). There was major variation in the reported delay within individual monogenetic diseases. Shorter delay was associated with disorders of childhood metabolism, immunity, and development. The majority (67.6%) of articles that studied delay reported an improvement with calendar time. Study design and definitions of delay were highly heterogenous. Three gaps were identified: (1) no studies were conducted in the least developed countries, (2) delay has not been studied for the majority of known, or (3) most prevalent genetic diseases.

CONCLUSION

Heterogenous study design and definitions of diagnostic delay inhibit comparison across studies. Future efforts should focus on standardizing delay measurements, while expanding the research to low-income countries.

Clinical updates in inborn errors of immunity: a focus on the noninfectious clinical manifestations

PURPOSE OF REVIEW

In the last 5 years, several new inborn errors of immunity (IEI) have been described, especially in the areas of immune dysregulation and autoinflammation. As a result, the clinical presentation of IEIs has broadened. We review the heterogeneous presentation of IEIs and detail several of the recently described IEIs with a focus on the noninfectious manifestations commonly seen.

RECENT FINDINGS

IEIs may present with early onset and/or multiple autoimmune manifestations, increased risk for malignancy, lymphoproliferation, severe atopy, autoinflammation and/or hyperinflammation. Because of this, patients can present to a wide array of providers ranging from primary care to various pediatric subspecialists. The International Union of Immunological Societies (IUIS) expert committee has created a phenotypic classification of IEIs in order to help clinicians narrow their evaluation based on the laboratory and clinical findings.

SUMMARY

Both primary care pediatricians and pediatric subspecialists need to be aware of the common clinical features associated with IEI and recognize when to refer to allergy-immunology for further evaluation. Early diagnosis can lead to earlier treatment initiation and improve clinical outcomes for our patients.

Disparities in Diagnosis, Access to Specialist Care and Treatment for Inborn Errors of Immunity

Inborn errors of immunity represent a rapidly expanding group of genetic disorders of the immune system. Significant advances have been made in recent years in diagnosis, including using genetic testing and newborn screening; treatment, including precision therapies, gene therapy and hematopoietic stem cell transplant; and development of patient registries to inform prevalence, understand morbidity of these disorders and guide the development of clinical trials. However, significant disparities due to age, race, ethnicity, socioeconomic status, or geographic location exist in all aspects of care of patients with inborn errors of immunity, beginning with delays in diagnosis and further compounded by impaired access to specialist care and treatment, leading to a notable impact on outcomes including morbidity and mortality. Addressing and correcting these disparities will require coordinated, deliberate and prolonged effort. Proposed strategies to improve equity at different levels include public health measures such as implementing universal newborn screening, supporting expanded health insurance coverage for diagnostic testing and treatment, improving access to novel therapeutics in low and middle income countries and developing artificial intelligence / machine learning tools to reduce delays in diagnosis, particularly in rural or less developed areas where access to specialist care is limited.

Inborn Errors of Immunity Associated With Type 2 Inflammation in the USIDNET Registry

Background

Monogenic conditions that disrupt proper development and/or function of the immune system are termed inborn errors of immunity (IEIs), also known as primary immunodeficiencies. Patients with IEIs often suffer from other manifestations in addition to infection, and allergic inflammation is an increasingly recognized feature of these conditions.

Methods

We performed a retrospective analysis of IEIs presenting with allergic inflammation as reported in the USIDNET registry. Our inclusion criteria comprised of patients with a reported monogenic cause for IEI where reported lab eosinophil and/or IgE values were available for the patient prior to them receiving potentially curative therapy. Patients were excluded if we were unable to determine the defective gene underlying their IEI. Patients were classified as having eosinophilia or elevated IgE when their record included at least 1 eosinophil count or IgE value that was greater than the age stratified upper limit of normal. We compared the proportion of patients with eosinophilia or elevated IgE with the proportion of samples in a reference population that fall above the upper limit of normal (2.5%).

Results

The query submitted to the USIDNET registry identified 1409 patients meeting inclusion criteria with a monogenic cause for their IEI diagnosis, of which 975 had eosinophil counts and 645 had IgE levels obtained prior to transplantation or gene therapy that were available for analysis. Overall, 18.8% (183/975) of the patients evaluated from the USIDNET registry had eosinophilia and 20.9% (135/645) had an elevated IgE. IEIs caused by defects in 32 genes were found to be significantly associated with eosinophilia and/or an elevated IgE level, spanning 7 of the 10 IEI categories according to the International Union of Immunological Societies classification.

Conclusion

Type 2 inflammation manifesting as eosinophilia or elevated IgE is found in a broad range of IEIs in the USIDNET registry. Our findings suggest that allergic immune dysregulation may be more widespread in IEIs than previously reported.