Disease severity classification and COVID-19 outcomes, Republic of Korea

Abstract

Problem

The surge in coronavirus disease 2019 (COVID-19) cases overwhelmed the health system in the Republic of Korea.

Approach

To help health-care workers prioritize treatment for patients with more severe disease and to decrease the burden on health systems caused by COVID-19, the government established a system to classify disease severity. Health-care staff in city- and provincial-level patient management teams classified the patients into the different categories according to the patients’ pulse, systolic blood pressure, respiratory rate, body temperature and level of consciousness. Patients categorized as having moderate, severe and very severe disease were promptly assigned to beds or negative-pressure isolation rooms for hospital treatment, while patients with mild symptoms were monitored in 16 designated facilities across the country.

Local setting

The case fatality rate was higher in the city of Daegu and the Gyeongsangbuk-do province (1.6%; 124/7756) than the rest of the country (0.5%; 7/1485).

Relevant changes

From 25 February to 26 March 2020, the ratio of negative-pressure isolation rooms per COVID-19 patient was below 0.15 in the city of Daegu and the Gyeongsangbuk-do province. In the rest of the country, this ratio decreased from 5.56 to 0.63 during the same period. Before the classification system was in place, eight (15.7%) out of the 51 deaths occurred at home or during transfer from home to health-care institutions.

Lessons learnt

Categorizing patients according to their disease severity should be a prioritized measure to ease the burden on health systems and reduce the case fatality rate.

Introduction

On 30 January 2020, the Director-General of the World Health Organization declared that the outbreak of the coronavirus disease 2019 (COVID-19) constituted a Public Health Emergency of International Concern.¹ By 15 August 2020, the global number of confirmed cases had increased to 21 million and the number of deaths had reached 755 566, translating into a case fatality rate of 3.6%.²

During an outbreak, the case fatality rate will depend on several factors, such as the demography of infected people, the number of infected people with a confirmed diagnosis and the health system’s capacity to cope with a rapid increase of cases.³ Thus, the case fatality rate varies among countries. For example, on 15 August the case fatality rate was far higher in France (15.2%; 30 275/198 876) than in the Republic of Korea (2.0%; 305/15 039).² Trying to keep the number of COVID-19 cases below the health system’s capacity of coping with such cases is one important strategy to keep the case fatality rate low.

In the Republic of Korea, the rapid surge of COVID-19 cases in the Gyeongsangbuk-do province, and especially in the city of Daegu, overwhelmed the local health system, leading to some patients having no choice but to wait at home for a hospital bed, or to be transferred to another area. On 26 March, these two areas had reported 83.9% (7756/9241) of all the confirmed cases in the country. The affected areas also reported a higher case fatality rate compared with the rest of the country – 1.6% (124/7756) versus 0.5% (7/1485), respectively.⁴ To ease the burden on the health system, the government implemented a disease severity classification system to identify the COVID-19 patients needing care. Here, we describe this classification system and analyse the relationship between the number of negative-pressure isolation rooms and COVID-19 deaths.

Local setting

In the Republic of Korea, the health-care resources are evenly distributed across the country and almost the entire population is covered by a single-payer national health insurance.⁵ This single-payer setting enables the government to swiftly decide on health policies. Before the outbreak, there were 1027 negative-pressure isolation rooms in the country, covering 52 million people.⁶

On 20 January 2020, the first case of COVID-19 was detected in the country, when a woman from Wuhan, China, was tested positive upon her arrival at Incheon International Airport, Seoul. In the month after the first case was detected, the cumulative number of cases slightly increased in the country. However, after the Shincheonji Church event on 18 February, the number of cases suddenly increased among its members and non-members who were infected by a member of this church.⁷ Until 1 March, 87.3% (3260/3736) of COVID-19 cases were directly or indirectly related to the church and concentrated in the city of Daegu and the Gyeongsangbuk-do province.⁴ The first COVID-19 death was reported on 20 February and the number of accumulated deaths has continuously increased after the cases surged and accumulated.⁴

Approach

On 1 March 2020, the government adopted a test, trace, treat strategy to cope with the outbreak.⁸ From the initial stage of the outbreak, the government made every effort to detect as many infected people as possible, to trace suspected cases using epidemiological investigation and to treat all people with a confirmed COVID-19 diagnosis.⁸

The health system response the government adopted can be summarized as follows.^8–10 First, the government secured health-care or other resources to detect, isolate and monitor people with clinical symptoms indicative of COVID-19 or having a confirmed COVID-19 diagnosis, and to treat patients with COVID-19. For instance, in cooperation with pharmaceutical companies the government promptly approved and adopted a diagnosis kit after Chinese authorities released the genetic sequences of the virus. Second, the government designated 74 hospitals dedicated to COVID-19 patients and secured 7500 beds in preparation for a surge in confirmed cases. Third, the government established a system to classify disease severity. This system was put in place to help health-care workers prioritize treatment for patients with more severe disease and to decrease the burden on health systems caused by COVID-19.⁸ On 1 March, the government published a guideline on how to classify confirmed cases into four categories: mild, moderate, severe, and very severe disease. After a person received a confirmed diagnosis, health-care staff in city- and provincial-level patient management teams classified the patients into the different categories according to the patient’s pulse, systolic blood pressure, respiratory rate, body temperature and level of consciousness (Table 1).¹¹ Patients categorized as having moderate, severe and very severe disease were promptly assigned to beds or negative-pressure isolation rooms for hospital treatment, while patients with mild symptoms were monitored in 16 designated facilities across the country, most of which are residential training centres of public institutions and private companies.⁸

Table 1. Disease severity classification system for COVID-19, Republic of Korea, 2020.

Criteria	Score
	0	1	2	3
Pulse, beats per min	51–100	41–50 or 101–110	≤ 40 or 111–130	≥ 131
Systolic blood pressure, mmHg	101–199	81–100	71–80 or ≥ 200	≤ 70
Respiratory rate, breaths per min	9–14	15–20	≤ 8 or 21–29	≥ 30
Body temperature, °C	36.1–37.4	35.1–36.0 or ≥ 37.5	≤ 35.0	NA
Level of consciousness	Normal	Voice reaction	Pain reaction	Non-reaction

COVID-19: coronavirus disease 2019; NA: not applicable.

Notes: Patients with a total score of 0–4 were classified as mild cases, moderate cases had a total score of 5–6, and severe and very severe cases had a score ≥ 7. Very severe cases were patients needing renal replacement therapy or extracorporeal membrane oxygenation.

To analyse the burden of COVID-19 on the health system’s capacity and its influence on COVID-19 deaths, we retrieved data from cases by date of illness onset of COVID-19 from 20 January to 26 March 2020 from the website of the Ministry of Health and Welfare.⁴ We separated the patients into two groups based on their residence: those living in the city of Daegu or the Gyeongsangbuk-do province and those living elsewhere in the country. We used data on the number of negative-pressure isolation rooms per identified cases of COVID-19 to measure the burden of COVID-19 on the health system.

Relevant changes

The changes in number of negative-pressure isolation rooms per COVID-19 patient and the case fatality rate is shown in Fig. 1. In areas not heavily affected by the outbreak, the number of negative-pressure isolation rooms per COVID-19 patient decreased from 5.56 on 25 February to 0.63 on 26 March. During the same period, the case fatality rate increased from 0.0% (0/169) to 0.5% (7/1485) in the areas not heavily affected by the outbreak. In the most affected areas, the health system was already overwhelmed on 25 February, with 0.12 negative-pressure isolation rooms per COVID-19 patient. The situation worsened and by 26 March there were only 0.01 rooms per patient. While the case fatality rate improved from 1.1% (8/724) on 25 February to 0.5% (17/3260) on 1 March, the rate was highest on 26 March (1.6%; 124/7756).

Fig. 1.

The capacity burden of COVID-19 and its outcomes in health systems in Republic of Korea, 25 February to 26 March 2020

COVID-19: coronavirus disease 2019.

Note: The most affected areas were in the city of Daegu and the Gyeongsangbuk-do province.

We also found that, from the onset of the outbreak to 8 March, out of the 51 deaths across the country, eight (15.7%) deaths occurred at home or during transfer from home to health-care institutions. However, no deaths have occurred outside a health-care facility since 8 March, which was 1 week after the government introduced the classification system.

Lessons learnt

After the classification system was in place, transferring patients with severe disease to health-care facilities in less affected areas became less common. Furthermore, isolating patients with mild symptoms in designated facilities protected the patients’ close contacts from being infected. Other efforts by the government, such as providing more resources to the affected area, also helped in controlling the outbreak.¹²

Based on the analysis, we learnt that a potential shortage of hospital beds, including negative-pressure isolation rooms, might lead to an increased case fatality rate. The affected area has a similar number of negative-pressure isolation rooms and beds in the intensive care unit per 1000 persons and an even higher number of hospital beds per 1000 persons compared to other areas. However, a surge in confirmed cases led to the affected area having a temporary shortage of hospital beds. Moreover, we observed that during the initial spread of the virus, deaths at home or during transfer from home to health-care institutions occurred. This finding implies that once a patient classification and referral system is established, deaths from COVID-19 can be reduced (Box 1).

Box 1. Summary of main lessons learnt.

• The government’s swift response was important in preventing a surge in confirmed cases leading to a shortage of beds.

• During an outbreak, the burden on a health system’s capacity is closely associated with the case fatality rate.

• A treatment system based on severity of disease to place priority on more severe cases helps with decreasing the burden on health systems.

Many countries are struggling to cope with the pandemic, and this problem is being aggravated by a lack of resources. In this context, experiences from the Republic of Korea could be used to illustrate ways in which to tackle the outbreak of COVID-19. Securing diagnostic kits, beds and health-care provision, as well as facilities dedicated to patients with COVID-19 across the country, are essential to detect cases, to isolate and monitor suspected cases, and to provide adequate health-care services. Furthermore, when health-care resources are lacking, measures to decrease the burden on health systems are needed. This study indicates that the burden on a health system’s capacity is associated with the case fatality rate, and suggests that allocating patients according to their disease severity should be a prioritized measure.