Association between race and in-hospital outcomes in children with spina bifida following inpatient urologic surgery

1 Introduction

Spina bifida (SB) is the most common permanently disabling birth defect in the US [1, 2]. This population requires routine urologic evaluation including surveillance of bladder function and upper tract evaluation [3, 4]. In order to treat or avert urologic complications, many individuals with SB undergo urologic reconstructive surgery such as bladder augmentation, catheterizable channel creation, or a bladder outlet procedure. However, these complex procedures carry a significant risk of in-hospital, post-operative complications. In a recent multi-institutional case series, the complication and readmission rates for SB patients undergoing laparotomy for urologic indications were 92%and 42%, respectively [5].

Previous reports have demonstrated that surgical complication rates may vary among racial and/or ethnic groups; specifically, that racial/ethnic minorities may be at higher risk of complications [6, 7]. In the setting of high overall complication rates among individuals with SB, a better understanding of potential effects of race and/or ethnicity would be helpful. Understanding the relative importance of these non-modifiable risk factors for complications would allow clinicians to identify at-risk populations and facilitate improvement of healthcare delivery at the system and patient level.

Thus, the primary objective of this study was to compare the odds of an in-hospital, post-operative complication among White, Black and Hispanic individuals with SB who underwent urologic surgery after accounting for available non-modifiable risk factors. The secondary objective was to compare length of stay (LOS) and cost among the same groups. The hypothesis was that the odds of in-hospital, post-operative complications, mean LOS, and mean inflation-adjusted costs would be lower in White SB encounters compared to their Black or Hispanic counterparts.

2 Methods

3 Results

In this administrative database analysis, Hispanic individuals with SB had an increase in inflation-adjusted cost and a longer LOS when compared to their White counterparts. The higher cost associated with the Hispanic pediatric encounters may be associated with the longer LOS. There was insufficient evidence to identify disparities of in-hospital post-operative complications, inflation-adjusted cost, or LOS between White and Black SB encounters.

Understanding the combination of disease-specific risk stratification and non-modifiable risk factors, including race and/or ethnicity, is important to provide more effective healthcare delivery in individuals with SB and to address inequalities on a system level. These findings demonstrate variation among racial/ethnic groups, specifically between Hispanic and White encounters regarding cost and LOS, although not in-hospital complications. This finding is particularly relevant given the increased incidence of SB in Hispanic populations, implying that Hispanic individuals may be disproportionately impacted both by SB and by complications from the surgical management of SB-associated neurogenic bladder. These findings echo a similar trend within the literature [7, 10–12]. Bloo et al. performed a meta-analysis comparing operative mortality and complications between minority groups and White patients in the general population. They found that minority groups were associated with longer post-operative hospital stays [6]. They also reported a higher risk of mortality and overall complication rate, which were not specifically addressed by the current study. The mechanisms driving these differences are probably complex and multifactorial. Explanations for racial/ethnic differences in surgical patients in other studies include socioeconomic status, presurgical risk, cultural factors, and biological/genetic factors [6, 10]. Likewise, it seems likely that other nonclinical factors, including geographic or population density cost differences, may be playing an as-yet unexplained role here.

This trend of racial/ethnic differences in post-operative outcomes has been previously reported in other pediatric urologic studies. Chu et al. noted racial differences in 30-day complication rates following urologic surgery in pediatric patients using the National Surgical Quality Improvement Program-Pediatrics (NSQIP-P). They found that non-Hispanic Black patients were at higher risk of 30-day complications and hospital-acquired infections compared to their non-Hispanic White counterparts [10]. That study included all urologic surgery patients under age 17 while the current study focused only on SB encounters. Additionally, it was a prospective study that bundled the specific post-operative complications with the procedure. It is possible that these findings in the general pediatric urology population are not as prevalent within the SB population. One explanation could be the organization and standardization of SB care. In the current study, 91%of patients had their surgery performed at urban, teaching hospitals. Many of these hospitals, including the authors’, provide a SB-specific multispecialty practice or participate in national registries to facilitate appointment scheduling and follow-up, provide multispecialty provider collaboration, and share outcome data across institutions [13, 14]. While these groups and registries do not specifically standardize surgical care of patients with SB, the data from these studies may be used to alter practice patterns and indirectly standardize care. Standardization of surgical care has been shown to decrease post-operative complications and may explain the inability to find sufficient evidence of a difference between racial/ethnic groups [15–18].

Perhaps most importantly, these findings must be interpreted in the context of this study’s design limitations. Length of stay is a multifactorial outcome that may be influenced by unmeasured variables such as patient, provider, or hospital system factors. The Nationwide Inpatient Sample represents a 20%stratified sample of US hospital admissions; therefore, the reported results may not be applicable to encounters beyond the database. Despite this, NIS does provide meticulous tracking of hospital weights and discharges to minimize the risk of sampling bias [19]. As with all retrospective, administrative databases, NIS may be affected by miscoding bias. The analysis relied on the accuracy of the diagnostic and procedure codes included in NIS; in particular, accurate diagnosis and racial/ethnic information was relied on in order to define this cohort and to identify post-operative complications. While the accuracy of NIS is high for an administrative database, it is possible that at least some portion of the cohort may be incorrectly coded. While it is not likely that this potential error is a source of bias impacting the results, a higher-than-expected degree of coding error among a particular racial/ethnic group could potentially have biased the results. Likewise, it is important to note that this NIS analysis was explicitly performed using ICD-9 data in order to limit miscoding bias during the era of the ICD-9 to ICD-10 changeover; the unintended consequence of this choice is that the data may be “out of date”. Future analyses using more recent NIS datasets would be of interest in order to verify these findings.

The analysis is subject to variability based on NIS reporting, which tracks encounters, not patients. Due to the rarity of SB and the number of years examined, it is possible that the same patient appeared multiple times and each encounter was treated as unique. This may result in overestimation of the prevalence of SB encounters or complications thereof. Similarly, because it is impossible to track a given patient across time, post-hospital outcomes and whether individual patients were readmitted or underwent repeat procedures were not assessed. Additionally, the picture of post-operative complications is limited by the inpatient-only nature of NIS, precluding analysis of outpatient encounters not captured in the database. Finally, it is assumed that any NSQIP-coded complication was a surgically-related complication, although there is a chance that comorbidity or unrelated medical illness could be at fault instead; if true, this would potentially result in overestimation of the complication rates. However, it can be assumed that such random events would have been dispersed equally among racial/ethnic groups. Alternatively, defining complications with NSQIP may underestimate the true overall complication rate as some complications may not be counted. However, use of NSQIP in post-operative patients is a well validated method to assess complications. Although ethnicity data is tracked separately for some HCUP databases, NIS provides only the Race variable, which considers Hispanic ethnicity as a “racial” group. Though patients may individually identify within multiple racial and ethnic groups, this categorization rendered them mutually exclusive to a specific racial group. Despite these limitations, NIS is rigorously monitored and audited for coding accuracy and represents a reasonably reliable panorama of the characteristics of an inpatient surgical cohort.

Though a difference in cost and LOS between Hispanic and White SB cohorts was detected, the basis of these differences was not able to be addressed due to the retrospective nature of the study and data limitations inherent to a large national administrative database. It is noteworthy that there were differences between encounters for Hispanic and White patients but not between encounters for Black and White patients. This is most likely due to unmeasured confounding or possibly to cultural responses to treatments/providers, but based on data limitations, this can only be speculated. In order to confirm and ideally move beyond these findings to address causality, more (ideally prospective) studies in this population are needed. Hopefully, future analyses will also be able to avoid NIS’s reliance on White race as a de facto comparator for other groups, and instead, adopt a more nuanced approach to a very complex research topic.

5 Conclusion

Hispanic ethnicity was associated with higher costs and longer LOS in pediatric SB surgical in-hospital encounters. A better understanding of the effect of these non-modifiable risk factors can help identify the need to address racial disparities and establish change at the individual practice and hospital system level.