The First Two Years of COVID-19 Hospitalization Characteristics and Costs: Results from the National Discharge Registry

1. Introduction

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was identified for the first time in the late 2019 in the city of Wuhan (Hubei, China). [1] It causes the coronavirus disease 2019 (COVID-19) with symptoms ranging from mild flu-like symptoms to severe pneumonia [2]. The World Health Organization (WHO) declared the outbreak a Public Health Emergency of International Concern from 30 January, 2020 to May 5, 2023 and a pandemic on 11 March 2020 [3]. The virus quickly spread all around the world, and during the first two years of the pandemic (January 2020 ro December 2021), the weekly updated WHO data reported 280,614,414 confirmed cases and 5,446,891 deaths1. One of the most significant social effects of the pandemic was its profound impact on hospital capacities worldwide [4]. In 2020-2021, the European Centre for Disease Prevention and Control (ECDC) reported 12,563,619 of Covid-19 hospitalizations in Austria, Belgium, Bulgaria, Cyprus, Czechia, Estonia, France, Ireland, Liechtenstein, Lithuania, Luxemburg, Netherland, Romania, Slovakia, Slovenia, Spain2. In the same period in US, the Centers for Disease Control and Prevention reported 3,719,818 hospitalizations in the whole country3. During the peaks of transmission, health systems in many countries were overwhelmed, and due to the complexity of treating COVID-19 patients, especially in intensive care units, hospitalization costs increased worldwide. A systematic review found that in Germany the total cost of hospitalization in intensive care per patient was 100,789 USD (5). Even if the world was not prepared nor coordinated to such emergency, there was an impressive mobilization of human societies worldwide. Virus lethality of the original strain was quickly estimated by the infection fatality ratio (IFR) assessed through several national serosurveys [6,7]. By the end of 2020, global Medicines Agencies had conditionally approved several vaccines based on different technologies, with others close behind (8,9). Most governments established unprecedented public health policies, such as social distancing, remote working, and lockdowns, to reduce the spread of the virus (10,11). Furthermore, there was an impressive proliferation of mathematical models aimed to predict and manage the pandemic as well as evaluate the implemented policies (12). Italy was the first European country to be hit by the new virus and declared a health emergency status from January 31, 2020 to the 31 of march 2022. The unexpected high speed of transmissions quickly caused hospitals saturation and forced the governmental administration to establish a national lockdown. The hardest period was during the first two years of pandemic, before the vaccination campaign (started in last days of 2020) began to have the desired effects. To increase the health system resilience, it is important to study hospitalizations and the related financial burdens due to COVID-19. This article is part of a broader project focused on assessing hospital characteristics associated with principal occupational respiratory diseases, including COVID-19, which is recognized as an occupational injury under specific conditions when contracted in the workplace. It aims to describe the COVID-19 hospitalizations in Italy and estimate the associated costs with these cases.

2. Methods

2.1. Settings

In Italy, the regional administrations have significant autonomy in managing and organizing healthcare services within their territories. They are responsible for allocating the funds received from the central government to hospitals (trough local health units) based on diagnosis-related group (DRG) and Major Diagnostic Categories (MDC) coding systems. Through a decree, The Ministry of Health establishes the National Standard Hospital Charges (NSHC) as the maximum cost per DRG (version 24) in cases of acute care and per MDC in cases of rehabilitation or long-term care cases. For each case defined above, it additionally establishes a length of stay threshold (t) beyond which an additional daily cost is incurred. An additional cost for COVID-19 hospitalizations, based on whether or not patients were admitted to intensive care, was established by the Ministry of Health's decree on August 12, 2021.

2.2. Participants

This study included all patients and their corresponding hospitalization episodes in Italy diagnosed with COVID-19 during the years 2020 and 2021.

2.3. Outcomes

The primary outcomes included the annual number of COVID-19 hospitalizations, along with the associated length of hospital stay and costs. Secondary outcomes were the characteristics of both the hospitals and the patients.

2.4. Data Sources/Measurement

The ministry of health provided two aggregated datasets from the National Discharge Registry for the years 2020-2021. The first dataset includes the number of patients by demographics, i.e. year, gender, and age groups (0 years; 1-4 years; 5-13 years; 14 years; 15-24 years; 25-44 years; 45-64 years; 65-74 years; 75+ years) and their residence at the regional level. The second dataset expands on this by including the number of hospital admissions and length of stay, categorized by the same demographic variables and further detailed by primary medical treatment (coded by ICD-9-CM), Diagnosis-Related Groups (DRGs, version 24) with distinctions between medical and surgical types, care activity (including pregnancy-related, acute care, long-term care, and rehabilitation), hospitalization regimen (ordinary or day-care), and outcomes at discharge (deceased, transferred, or discharged to residence). For analytical purposes, we combined the age groups 5-13 and 14 years into a single group (5-14 years) and categorized regions into Territorial divisions (North-West, North-East, Centre, South, and major Islands) to facilitate regional comparisons. From the 2020 and 2021 annual discharges reports of the Ministry of Health, we took the total number of hospitalizations, the days of length of stay and the total estimated cost (13,14). Following costs estimates in those reports, we applied the National Standard Hospital Charges (NSHCs) as defined by the Ministry's decree of October 12, 2012 and thresholds (t) as specified in the decree of December 18, 2008. For acute care, NSHC charges are cumulatively expressed for the entire period up to the threshold time and as a daily charge for any period beyond this threshold. For rehabilitation and long-term care, NSHC charges are consistently expressed as daily charges, applicable both within and beyond the threshold period. Since we lack a variable indicating admission to intensive therapy, we have used ICD-9-CM treatment codes, specifically 96.7 (other continuous invasive mechanical ventilation), as a proxy for an intensive care stay. We downloaded the Italian population by age and Territorial division (Northwest, Northeast, Central, South, and Islands) from the site of the Italian Institute of Statistics4. Statistics about the whole Italian hospitalizations (number of admissions, length of stay and estimated costs) were taken from the Ministry of Health reports (13,14).

Statistical Analysis

We began by aggregating episodes of hospitalization that resulted in death at discharge, based on patient characteristics. This aggregated data was then merged with the existing patient database to incorporate the number of deceased patients. Within this enhanced dataset, we analyzed the rate of hospitalized patients per population, segmented by year, age, and Territorial division. Additionally, we calculated the percentages of deaths and of male patients.

For the hospitalization dataset specifically, we examined the number of admissions and the total days of hospital stay, along with their respective proportions of the total hospital admissions. Cost assessment was conducted in several steps using the aggregated dataset, which includes the number of admissions (n) and days of stay (GG), segmented by the previously mentioned variables. For each record, based on NSHC charges and threshold times, we associated the corresponding charges within (ch1) and beyond (ch2) the threshold and calculated the cumulative threshold (T) for grouped admissions as:

T = t × n

The total number of days exceeding the threshold (diff) for the corresponding admissions was determined by:

diff = min{0,GG-T},

Costs of admission for acute care (TCA) were then assessed using the formula:

TCA = (ch₁ + diff × ch₂) × n

Similarly, for rehabilitation and long-term care admissions (TCRL), costs were calculated as:

TCRL = (min{GG,T} × ch₁ + diff × ch₂) × n

We also added an extra cost of 3,713 × n euros to all group of admissions which were not transferred and 9,697 × n of euros to all group of admissions with principal treatments coded as 96.7 in ICD-9-CM. Since the general expenses in the reports (13,14) are calculated net of the extra costs attributed to COVID-19, we added to them our estimates. Finally, 2020 costs were deflated by means of annual consumer price indexes provided by the Italian National Institute of Statistics.

3. Results

Patients’ Characteristics

During the initial two years of the COVID-19 pandemic (2020-2021), there were 298,856 hospitalized patients in 2020 and 333,447 in 2021, with a significant concentration in the northern regions, especially during the first year. The hospitalization rate in Northern Italy was twice that of the rest of the country. Females were more prevalent in the 15-44 age group, while males dominated other age groups. Hospitalization rates varied by age, exhibiting a sine wave pattern with peaks observed in infants and the 65-74 years age groups. Mortality rates increased with age, remaining below 3% for individuals under 44 but rising exponentially in older age groups, surging to 40% in those of 75 and older (Table 1).

Hospitalizations Characteristics

The high number of transfers increased the total number of hospitalizations attributed to COVID-19 to 357,354 in 2020 and 399,043 in 2021, representing 5.6% and 5.8% of all admissions, respectively (Table 1). Patients admitted for COVID-19 experienced a transfer rate three times higher (16-17% vs. 5.5-5.7%) than those hospitalized for other reasons. Excluding transfers, COVID-19 admissions and their relative percentages dropped to 4.8% and 5.1% for 2020 and 2021, respectively (Table 1 of supplemental materials). The total days of hospital stay for COVID-19 patients were 4,918,162 in 2020 (10% of the total) and 5,911,253 in 2021 (12% of the total). The mean length of stay was 13.8 days in 2020 and 14.8 days in 2021 for COVID-19 hospitalizations, compared to 7.1 and 6.8 days for other discharges, respectively (Table 2). COVID-19 hospitalizations were almost all in acute care (94% in both years), only a little part underwent to surgical treatments (6.7% in 2020 and 8.4 % in 2021) and day hospital almost tripled in 2021, from 1.1% to 2.9% (data not showed in tables).

Hospitalizations Costs and Intensive Care

The estimated total cost for COVID-19 hospitalizations in 2021 euros was 3,971,105,146, in 2020 (11,112 per admission and 807 per day) and 4,989,271,574 in 2021 (12,503 per admission and 844 per day). Without considering the extra financial burden attributed to COVID-19, the hospitalization cost would have been 2,825,083,197 in 2020 (7,906 euros per admission and 574 euros per day) and 3,690,268,358 in 2021 (9,248 euros per admission and 624 euros per day) (Table 3). COVID-19 Hospitalizations with other continuous invasive mechanical ventilation as the principal treatment were 18,143 (5.1%) in 2020 and 21,255 (5.3%) in 2021. The corresponding mean lengths of stay were 17.5 and 19.7 days, respectively. Compared to other COVID hospitalizations, the length of stay increased by an average of 4 days in 2020 and by 5 days in 2021 (Table 3). Hospitalizations costs for patients with invasive mechanical ventilation amounted to 429,351,427 euros (23,665 euros per admission and 1,355 euros per day) in 2020 and 514,945,622 euros (24,227 euros per admission and 1,229 euros per day) in 20221 (Table 4). The extra financial burden increased the cost of these admissions about of 40%. For the other COVID-19 hospitalizations, the total costs were 3,541,753,719 euros in 2020 (10,441 euros per admission and 770 euros per day) and 4,474,325,952 euros in 2021, with costs per admission and per day also increasing to 11,843 euros and 815 euros, respectively. The extra financial burden increased the cost of these admissions about of 25%.