Product type and the risk of inhibitor development in nonsevere haemophilia A patients: a case-control study

Nonsevere Hemophilia: The Need for a Renewed Focus and Improved Outcomes

People with nonsevere hemophilia (PWNSH) are phenotypically more diverse than those with severe hemophilia. Perceptions relating to a "nonsevere" phenotype have contributed to fewer research initiatives, fewer guidelines on optimal management, and a lack of standards for surveillance and clinical assessment for affected individuals. In many cases, episodes of abnormal bleeding could, if investigated, have led to earlier diagnosis. Furthermore, the major recent developments in therapy for hemophilia have largely focused on severe disease and, as a group, PWNSH have not been included in many key clinical trials. Benefiting people with severe disease, innovative replacement therapies have generally targeted factor levels that are above those present in a large proportion of PWNSH. Therapeutic advances can lead to improvement in phenotype for people with severe hemophilia over that currently experienced by many PWNSH. As a result, we are approaching a point where PWNSH may, in many countries, have a higher risk of bleeding and restriction in lifestyle than those with severe disease but with more limited therapeutic options. Given the multiple major advances in treatment for people with hemophilia, it is timely to review the aspects of nonsevere disease, to ensure equity in care and management for all individuals with this condition.

Mutational landscape, inhibitor development, and health-care burden in non-severe haemophilia A: A single-centre Australian experience

AIM

To characterise non-severe haemophilia A (HA) patients enrolled on the Australian Bleeding Disorders Registry (ABDR) treated through a state-wide Haemophilia Treatment Centre (HTC) with respect to their mutational profile, inhibitor risk and health-care burden.

METHOD

We conducted a single-centre observational study of all non-severe HA patients treated at the Alfred Health HTC registered on the ABDR as of the 26th July 2023. Data were extracted from the ABDR and electronic medical record (EMR) regarding demographics, severity, genetic testing, treatment, inhibitors, bleeding events and procedures. Inhibitor risk was calculated as a function of exposure days (EDs) of FVIII replacement.

RESULTS

There were 289 non-severe HA patients treated at the Alfred HTC registered on the ABDR as of July 2023, all of whom were adult patients aged > 18 years old. Genotyping had been performed in 228/289 (78.9%). Of the inhibitor analysis population, 14/193 (7.3%) had an inhibitor. The cumulative incidence of inhibitor development at 75 EDs was 31% (95% CI 13%-46%). The median cost of bypassing agents per inhibitor patient was $57,087.50/year.

CONCLUSION

These results demonstrate a relatively high inhibitor prevalence and incidence risk in non-severe HA compared to previously published work, although this may partly reflect a smaller population size. High rates of genotyping have allowed representative mutational characterisation. The burden of care imposed by non-severe HA in terms of bleeding events, procedures and bypassing agent cost is larger than expected, particularly within the inhibitor population.

Nonsevere hemophilia A: often overlooked, but not forgotten

PURPOSE OF REVIEW

Nonsevere hemophilia A (NSHA) patients have received relatively little clinical and research attention as compared with their severe counterparts. There is increasing recognition that despite their milder bleeding phenotype, the management of NSHA can be a challenge, with most management decisions largely inferred from severe hemophilia A data. This review focuses on some of the more recent developments in the field of NSHA.

RECENT FINDINGS

Epidemiologic studies suggest that NSHA remain under-recognized and under-diagnosed globally. As the NSHA population ages, they are susceptible to age-related comorbidities. Large cohort studies of NSHA report that the most common primary cause of death is malignancy. NSHA patients have a lifetime risk of inhibitor development with increasing exposure to factor VIII concentrate. Even so, not all patients with inhibitors will require eradication treatment, irrespective of bleeding phenotype at time of inhibitor development.

SUMMARY

As there are currently no evidence-based strategies for inhibitor eradication in NSHA patients, preventive strategies are critical to mitigate inhibitor risk in NSHA. There is a need for active surveillance of NSHA patients by hemophilia treatment centers to address hemophilia-related issues and other age-related comorbidities, in collaboration with primary care physicians and other subspecialists.