Clinical and Economic Burden of Systemic Lupus Erythematosus in the Years Preceding End-Stage Kidney Disease Diagnosis: A Retrospective Observational Study

This retrospective, observational study showed that patients with SLE incurred substantial clinical burden, HCRU and healthcare costs in the 12 months pre-ESKD diagnosis, with HCRU and healthcare costs increasing from 5 years to 1 year pre-ESKD. This highlights the need for early intervention for patients with SLE with the aim of preventing disease progression and worsening of renal function.

Renal outcomes became more common and severe as patients approached their ESKD diagnosis, with the proportion of patients with renal involvement and LN increasing from year 5 to year 1 pre-ESKD diagnosis. Additionally, the proportion of patients with comorbidities increased in the years preceding ESKD; specifically, the majority of patients had a diagnosis of hypertension in the year pre-ESKD diagnosis. A similar increase in the proportion of patients requiring radiologist and nephrologist visits was also observed. Most patients had severe SLE and the mean number and severity of SLE flares increased as patients approached their ESKD diagnosis. This may have contributed to the deterioration in kidney function, as each subsequent flare reduces the lifespan of the kidney [4, 9].

According to the European Alliance of Associations for Rheumatology and European Renal Association–European Dialysis and Transplant Association (EULAR/ERA-EDTA) recommendations for LN, patients with SLE with any signs of kidney involvement (such as proteinuria ≥ 0.5 g/24 h and/or an unexplained decrease in glomerular filtration rate) should be considered for a kidney biopsy to confirm suspected LN diagnosis [18]. A significant fraction of biopsies is performed by radiologists [19]; however, in this study, we observed a low rate of kidney biopsies compared with radiologist visits in the 12 months pre-ESKD (20.6% vs 75.7% of patients, respectively). As patients approach their ESKD diagnosis, they are at an advanced stage in their disease course and their eGFR is likely to be less than 25 ml/min/1.73 m2 [20]; biopsies may be precluded in these instances as information critical to the management of their disease is unlikely to be obtained. Another explanation for the low rate of kidney biopsies may be that biopsies were performed prior to the observation period. This suggests that all biopsies that were conducted may not have been captured in this study.

Mean total healthcare cost per patient was $64,887 in the 12 months pre-ESKD diagnosis. This is consistent with findings reported in a previous study that showed annual healthcare cost was up to $52,951 per patient with severe SLE [21]. Furthermore, most of the costs were attributed to inpatient admissions and outpatient care, consistent with the results reported in a previously published retrospective study of economic outcomes in patients with SLE in the USA [16].

Additionally, we have demonstrated that the healthcare costs progressively increased from year 5 to year 1 pre-ESKD diagnosis. In particular, inpatient costs were markedly increased in the year before diagnosis, likely as a direct result of declining kidney function and increasing comorbidities.

Pharmacy fills, followed by ambulatory visits (physician office and hospital outpatient), constituted the greatest HCRU in the 12 months pre-ESKD diagnosis, consistent with reports of a previous study that showed pharmacy fills and outpatient visits were the most significant source of HCRU among patients with SLE [22]. Additionally, the increased use of oral corticosteroids and immunosuppressants may have caused more infections and infestations due to their immunosuppressive properties [23, 24] and, in turn, contributed to an increased rate of hospitalisations pre-ESKD diagnosis, as reflected by the results of this study.

These findings highlight the substantial downstream healthcare burden of patients with SLE who develop LN and progress to ESKD, emphasising the need for early intervention among patients with LN, which may mitigate disease progression. One study has previously identified that early diagnosis among patients with SLE is associated with lower inpatient and corresponding SLE-related hospitalisation costs compared with those with a late diagnosis [25]. In addition, data from the Hopkins Lupus Cohort showed that patients who achieved a renal response (defined as an eGFR ≤ 20% below baseline value or ≥ 60 ml/min/1.73 m2 or urine protein/creatinine ratio ≤ 0.7 g/day) had a lower risk of ESKD or death and chronic renal insufficiency over a median follow-up of 6 years compared with patients without a renal response [26]. These results further suggest that early diagnosis and treatment to improve renal responses may prevent disease progression, the long-term sequelae and burden associated with LN.

This study had several limitations that are common to retrospective observational claims-based studies. Firstly, evidence of an SLE or ESKD diagnosis was available only from ICD-9-CM or ICD-10-CM codes associated with medical claims; these codes are subject to possible misspecification if diagnostic codes are inaccurate or misclassified. Additionally, the use of an algorithm to classify SLE disease severity does not necessarily provide an accurate indication of disease activity or organ damage. Similarly, the algorithm used to identify the incidence and severity of flares relies on the patient’s use of healthcare services and prescriptions of SLE medications; despite this, the algorithm is a validated way of capturing flare data [17, 27]. Some patients are only diagnosed with SLE once they have developed manifestations, such as LN. The cost of care of these patients may be greater compared with those with pre-existing SLE; however, the cost of these patients specifically has not been captured. The definition of patients with LN was also based on the presence of renal diagnosis codes on medical claims, rather than biopsy-confirmed LN or renal laboratory results. Additionally, renal involvement was identified on the basis of the presence of specific diagnosis codes on medical claims. As a result of the limitations of claims-based data noted above, it is not possible to determine whether ESKD was caused by LN or other renal involvement in this population. Furthermore, race and ethnicity data were not available in this data set; therefore, analysis to determine the effect of race or ethnicity on these outcomes could not be conducted, despite being known predictors of increased SLE disease incidence among patients of Black African ancestry [28]. This study lacked comparators, such as patients with ESKD but with no SLE; thus, statistical comparisons with other patient populations could not be conducted. Nonetheless, this study demonstrates the economic burden (measured in terms of HCRU and associated costs) in patients with SLE who are approaching ESKD diagnosis, providing a better understanding of the ESKD burden at a population level in a routine clinical practice setting. Finally, only patients with insurance coverage were included in the study, which may limit the generalisability of these outcomes to the uninsured population. However, despite its limitations, this study retrospectively followed a sizable cohort of patients with SLE over 5 years, providing a comprehensive and real-world depiction of their clinical burden, treatment patterns, HCRU and healthcare costs over time.

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