Gout and rheumatoid arthritis (RA) are the two most common forms of chronic inflammatory arthritis worldwide, with both being characterized by acute flares. Although these diseases can be optimally treated in an outpatient setting, both still require emergency department (ED) visits or hospitalizations in some cases, leading to substantial healthcare costs. With the development of biologic drugs and the standardization of treatment strategies, the hospitalization rate of RA has been declining. One study found that the hospitalization rate of Canadian patients with RA decreased by 49% from 2000 to 2011, while it decreased from 13.9 to 4.6 per 100,000 adults in the United States from 1993 to 2011 [1,2]. On the other hand, the number of patients with hospitalization for gout doubled from 3.8 to 7.6 per 100,000 Canadian adults and from 4.4 to 8.8 per 100,000 United States adults, reflecting an increase in prevalence and poor quality of care since suboptimal management of chronic diseases is often reflected in ED visit statistics. One study using US Nationwide Emergency Department Sample data showed that acute gout accounted for 0.2% of all ED visits and $166 million in ED charges in 2008 [3]. A more recent study reported a 14% increase from 2006 to 2012 [4], while another study found that both the absolute number of ED visits and the cost per visit increased over time in the United States [5]. Hyperuricemia and gout have a high prevalence in Asian countries [6], and the financial burden of RA is constantly increasing. Despite this, only a few studies have examined the pattern of healthcare utilization or ED visits for gout or RA in this region.

The objective of the present study was to examine temporal trends in hospital visits and healthcare costs for gout using a nationally representative sample as well as to compare them with equivalent trends for seropositive RA. RA was chosen for comparison because both gout and RA are ambulatory sensitive care conditions, and the use of ED or hospitalization might reflect suboptimal disease control.

We hypothesized that, over the past decade, gout and RA showed contrasting trends in this regard and that each condition could serve as the other’s internal comparison group.

During the study period (2010–2017), the datasets included a total of 2,777,017 gout patients and 801,590 seropositive RA patients (raw data) (Supplementary Table 1).

Gout is one of the most common chronic diseases affecting adults, and its prevalence has almost doubled over the last few decades [8]. In a recent study, the prevalence and incidence of gout varied widely according to the population studied and methods employed but ranged from a prevalence of < 1% to 6.8% and an incidence of 0.58 to 2.89 per 1,000 person-years [9]. At the same time, it is a condition that can be effectively managed using currently available medications. However, suboptimal care for patients with gout leads to acute flares, which then results in ED visits or hospitalizations. Thus, the pattern of ED utilization and hospitalization might reflect the level of care for gout [3].

In the present study, the annual rate of ED visits for gout increased by 3.8 times from 2010 to 2017, while that of ED visits for seropositive RA increased by 1.49 times. Conversely, the annual increase in the hospitalization rate for gout was less pronounced at 26%. The increase in ED visits for gout was highest among those between 30 and 50 years of age, while that for seropositive RA was highest among those aged ≥ 70 years.

Two studies reported an increase in ED visits for gout in the United States [4,5]. A study using US National ED Sample data showed that ED visits and costs increased from 2009 to 2012, with total ED visit charges increasing by 47%. A serial cross-sectional analysis of the same DB showed that the rate of ED visits for gout increased by 14% between 2006 and 2012. The increase was most pronounced (29%) in those aged 45 to 54 years. On the other hand, a study within a single healthcare system in Hawaii reported that the rates of gout ED visits in 2017 trended downward and that they had significantly decreased since 2011 [10]. The rates of RA outpatient visits, which were used as an internal comparison group, also decreased in 2017, as did the rates of outpatient and inpatient visits for gout. Therefore, these results reflect a change in the overall healthcare utilization pattern, rather than a true decrease in ED visit rates among patients with gout. In addition, patients with gout had higher rates of ED visits than those with RA, suggesting that gout care may be suboptimal in Hawaii. To our knowledge, the present study is the first to examine the use of ED for gout in a Korean population. We found a larger increase in the annual rate of ED visits for gout than in previous studies done in the United States. In a study using the National Health Claims DB, the prevalence of gout in Korea nearly doubled from 2007 to 2015 (3.49 vs. 7.48 per 1,000 persons), and the incidence of gout was growing faster in the young population than in the older population [11]. However, the increase in ED visit rate for gout was higher even after taking the increase in prevalence into account. In particular, the cause of the spike from 2015 to 2016 was unclear. The Korea National Health and Nutrition Examination Survey (KNHANES) found that men in their fourth decade had the highest rate of alcohol intake and excessive caloric intake [12,13], which may partly explain the high ED visits in this age group. Although suboptimal hyperuricemic control might lead to frequent attacks and ED visits, the factors contributing to ED visits for gout have not been studied. Therefore, the factors that lead to ED visits for gout must be examined, including medication use and abrupt lowering of uric acid levels, which we plan to address in a future study. In a previous survey study of United States primary care physicians, only half of primary care providers reported optimal treatment practices for the management of acute gout [14]. In addition, non-compliance with the treatment guidelines by clinicians in real practice may lead to an increase in ED visits for gout, and it would be helpful to see if the physicians followed the guidelines for gout treatment in real practice [14–16]. Because interruption of urate-lowering therapy (ULT) during gout flare was also found to lead to ED visits for gout [16], it is important to educate gout patients who regularly take ULT regarding adherence.

During the study period, the annual healthcare cost per outpatient visit and hospitalization for gout increased, whereas the ED visit costs for gout decreased. This is in contrast to United States studies. It is hypothesized that recent increases in visits may be mostly due to acute attacks, which are more easily treated than other complications such as infection or adverse drug effects.

Among patients with seropositive RA, the rate of ED visits also increased during the observation period but was less pronounced than in those with gout. In the sex- and age-specific analysis, the ED visits for seropositive RA did not increase except for the oldest age group, suggesting that patients with RA were better managed in the outpatient setting than those with gout in younger age groups. The doubling of the cost per visit for outpatients with seropositive RA may have occurred because the drug cost increased after the use of biologic agents. Another study showed that the healthcare cost for RA in Korea nearly doubled from 2004 to 2013, which was in line with our results [17].

The present study had several limitations. We used the HIRA DB, which provides analyzed partial data for all patients with the disease of interest rather than the full data for each patient. Thus, we could not analyze risk factors for flares of gout, such as individual serum uric acid level, concomitant medications (allopurinol or febuxostat), or dietary intake, and it was not possible to confirm the reason for ED visit. Second, for the diagnosis of gout and seropositive RA, the ICD-10 codes could not be validated. Diagnostic codes based on claims data that are collected with the purpose of reimbursing healthcare services, and not for clinical purposes, may not match the actual disease. In particular, in the case of mild disease such as gout, it is possible that more information other than the actual diagnosis code was included. To confirm the diagnosis of the disease, an operational definition using prescribed medications may also be considered. Finally, because only seropositive RA was included, not all hospital visits for RA were identified. However, using the national health claims DB, we could assess the prevalence of healthcare usage for gout among the general Korean population. We plan to examine the factors associated with ED visits for gout patients in a future study, which would elucidate possible choices for optimization of treatment of gout and guide policy decisions. Many studies have addressed the prevalence of ED visits for gout in Western countries [2,5,10,18–20], but very little research has been carried out in Asian countries. The present study was the first to analyze hospital visits due to gout in Korea.

In conclusion, between 2010 and 2017, the prevalence of ED visits for gout increased more than that of ED visits for seropositive RA in the Korean population. The NHIS should consider this trend and focus on the optimal management of gout in the outpatient healthcare setting.