Impact of deficiency anaemia comorbidity in generalized pustular psoriasis hospitalizations.

Abstract

Generalized pustular psoriasis (GPP) is a rare heterogeneous cutaneous disease characterized by multiple flares of painful pustules with widespread inflammation.1 Chronic systemic inflammation in GPP may result in anaemia by mechanisms such as iron sequestration in macrophages.2 Lee et al.3 demonstrated an increased risk of psoriasis in chronic kidney disease patients with low haemoglobin levels. Though some level of associations between anaemia and GPP has been previously considered, we sought to evaluate whether the presence of anaemia was associated with adverse inpatient outcomes in patients hospitalized with GPP. We reviewed the National Inpatient Sample, a publicly available, de-identified database of US hospital encounters produced by the Agency for Healthcare Research and Quality (AHRQ), from the years 2016 to 2020. GPP diagnosis was identified by searching for International Classifications of Disease, 10th Edition (ICD-10-CM) code L40.1 (generalized pustular psoriasis) as a primary diagnosis. We utilized the AHRQ Elixhauser Comorbidity Software Refined (CMR) to identify deficiency anaemia comorbidity. A full list of ICD-10-CM codes categorized under deficiency anaemia can be viewed in Table S1. The CMR was used to search for the presence of leukaemia, lymphoma, metastatic cancer, solid tumor without metastasis and in situ/malignant. Demographic characteristics including age, sex, race, income, insurance status and outcome measures of length of hospital stay and cost of inpatient visit were collected. Cost was standardized between hospitals using cost-to-charge ratio files. Patients under the age of 18 were excluded. The sample was separated into cohorts by the presence or absence of a deficiency anaemia comorbidity. Univariate analysis was conducted between groups using the Wilcoxon rank-sum test for complex survey samples and chi-squared test with Rao & Scott's second-order correction. Multivariate linear regression analysis was conducted to evaluate the effect of anaemia comorbidity on length of stay and cost of care after controlling for demographic factors and malignancy status. A total of 860 GPP hospitalizations were identified with 120 individuals having any form of deficiency anaemia as a comorbidity. Of individuals with a deficiency anaemia comorbidity, 65 individuals had a diagnosis of anaemia, unspecified (ICD-10-CM: D64.9). The mean length of stay and cost of care for the anaemia cohort was 9.6 days (SD: 6.6) and $14 919 (SD: 10 075), respectively. The non-anaemia cohort had an average length of stay of 5.2 days (SD: 5.0) and average cost of $9862 (SD: 128 38). Length of stay (p < 0.001) and cost of care (p < 0.001) were significantly different across the two groups in univariate analysis (Table 1). The multivariate linear regression additionally demonstrated significantly longer lengths of stay (p < 0.001) and cost of hospitalization (p = 0.019) after controlling for demographic variables and presence of a malignancy (Table S2). Our study observed increased costs of care and length of stay for GPP hospitalizations among patients with associated deficiency anaemias. While previous studies have evaluated the effects of altered iron status on psoriasis, studies assessing the impact of anaemia comorbidity on GPP hospitalization outcomes are limited.4 Though our study utilizes the strengths of a robust national dataset, there are several limitations that should be considered. First, GPP and anaemia were identified using the ICD-10-CM code, which may not have captured all cases, specifically those with mild or later diagnosed cases. Additionally, due to the cross-sectional nature of this study, only an association can be identified without a causative relationship, as there may be other comorbidities present in these patients that may influence patient outcomes. Finally, the data are limited to the U.S. healthcare context and may not be generalizable to other countries. However, a biologically plausible explanation for the findings—that more severe cases of GPP are associated with systemic comorbidities such as anaemia—is worth exploring in other national datasets if available. Our findings warrant further studies on the mechanism behind GPP pathogenesis and treatments as well as how associated anaemia influences disease outcomes beyond lengths of stay and costs of care. SP, KY, RM, SNS and VEN contributed to designing the research study, performing the research and the writing of the manuscript. SP constructed Table 1, Tables S1 and S2. All authors have read and approved the final version of the manuscript. None. None. The data that support the findings of this study are available in Agency for Healthcare Research and Quality at https://www.hcup-us.ahrq.gov/db/nation/nis/nisdbdocumentation.jsp. These data were derived from the following resources available in the public domain: Healthcare Cost and Utilization Project, https://www.hcup-us.ahrq.gov/db/nation/nis/nisdbdocumentation.jsp. Tables S1–S2 Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.