Underlying diseases là gì

Background

Mortality prediction of pneumonia by severity scores in patients with multiple underlying health conditions has not fully been investigated. This prospective cohort study is to identify mortality-associated underlying health conditions and to analyse their influence on severity-based pneumonia mortality prediction.

Methods

Adult patients with community-acquired pneumonia or healthcare-associated pneumonia [HCAP] who visited four community hospitals between September 2011 and January 2013 were enrolled. Candidate underlying health conditions, including demographic and clinical characteristics, were incorporated into the logistic regression models, along with CURB [confusion, elevated urea nitrogen, tachypnoea, and hypotension] score as a measure of disease severity. The areas under the receiver operating characteristic curves [AUROC] of the predictive index based on significant underlying health conditions was compared to that of CURB65 [CURB and age  65] score or Pneumonia severity index [PSI]. Mortality association between disease severity and the number of underlying health conditions was analysed.

Results

In total 1772 patients were eligible for analysis, of which 140 [7.9%] died within 30days. Six underlying health conditions were independently associated: home care [adjusted odds ratio, 5.84; 95% confidence interval, CI, 2.2814.99], recent hospitalization [2.21; 1.363.60], age  85years [2.15; 1.084.28], low body mass index [1.99, 1.253.16], neoplastic disease [1.82; 1.172.85], and male gender [1.78; 1.162.75]. The predictive index based on these conditions alone had a significantly or marginally higher AUROC than that based on CURB65 score [0.78 vs 0.66, p = 0.02] or PSI [0.78 vs 0.71, p = 0.05], respectively. Compared to this index, the AUROC of the total score consisting of six underlying health conditions and CURB score [range 010] did not improve mortality predictions [p = 0.3]. In patients with one or less underlying health conditions, the mortality was discretely associated with severe pneumonia [CURB65  3] [risk ratio: 7.24, 95%CI: 3.0825.13], whereas in patients with 2 or more underlying health conditions, the mortality association with severe pneumonia was not detected [risk ratio: 1.53, 95% CI: 0.942.50].

Conclusions

Mortality prediction based on pneumonia severity scores is highly influenced by theaccumulating number of underlying health conditions in an ageing society. The validation using a different cohort is necessary to generalise the conclusion.

The burden of pneumonia is increasing in societies with ageing populations, despite guideline-based standard management [1, 2]. In Japan, people have direct and around-the-clock access to high quality medical care under the Universal National Health Insurance Coverage, but pneumonia mortality is steadily rising and the disease is now ranked third as a cause of death [3]. In a society with an ageing population, pneumonia death rates show two major distributions, with one subgroup containing previously healthy patients with overwhelming septic shock or multiple organ failure, and the other containing patients with multiple underlying health conditions for death [4]. This rise in mortality is thought to be due to the increase in the latter subgroup [5, 6]. Most of underlying health conditions are age-related chronic factors, such as comorbid illnesses, swallowing dysfunction, healthcare-associated morbidities or changes in immune function [7,8,9,10], which are not easily or quickly modified by treatment.

An accumulating number of studies have evaluated severity scores, ie. CURB65 [confusion, elevated blood urea nitrogen, tachypnoea, hypotension, and age  65] or Pneumonia Severity Index [PSI], for mortality prediction and severity-stratified decision-making for hospitalisation [11,12,13,14]. Predictor variables used in those models have mainly been parameters directly related to pneumonia severity, such as respiratory rate, blood pressure, consciousness level, oxygen saturation, or several laboratory or radiological test results, all of which are modifiable by appropriate management of pneumonia. However, in a population setting where a significant number of people have multiple underlying health conditions, we hypothesised that pneumonia severity scores alone should have a limitation of predicting mortality, and that co-evaluating underlying health conditions which patients already have before they contract pneumonia should provide more comprehensive mortality assessment. We found no study exclusively evaluating the influence of underlying health conditions on severity-based pneumonia mortality prediction.

This study is aimed to identify mortality-associated underlying health conditions independent of pneumonia severity among adult pneumonia patients and to evaluate how these conditions influence on mortality prediction based on pneumonia severity scores. We analysed data from a cohort of patients enrolled in a prospective multicentre surveillance for community-acquired pneumonia [CAP] and healthcare-associated pneumonia [HCAP] in Japan [15]. We focused on clinical conditions obtainable by simple history-taking and basic examination at initial patient contact, making the results applicable in primary clinical settings, including busy emergency rooms.

Study setting, design, and sites

The Adult Pneumonia Study of Japan was a two-year prospective multicentre study which began in September 2011 at four community hospitals in Japan. [15]

According to the national statistics in 2012, 25.1 and 3.6% of the Japanese population were aged 65 and  85years, respectively [3]. The estimated coverage rate of the 23-valent polysaccharide pneumococcal vaccine for adults was 17.5% in 2012 [16]. Initial empiric antibiotic treatment for CAP and HCAP is informed by the guidelines of The Japanese Respiratory Society, which generally follow the international guidelines [17]. The current analysis was based on a dataset which had been used in our previous work [15]: the data had been collected between September 2011 and January 2013.

Patient enrollment

All patients who visited the outpatient department of or were admitted to our hospitals were enrolled if they fulfilled all of the following criteria: 1] aged 15; 2] symptomology compatible with pneumonia [e.g., fever, cough, sputum, pleuritic chest pain, dyspnoea]; 3] new pulmonary infiltrates by chest X-ray [CXR] or computed tomography [CT] scan images consistent with pneumonia. All CXR and CT scan images were reviewed by multiple clinicians on-site and consensus interpretations were recorded. If a patient developed the disease more than 48h after hospitalisation, the patient was classified as having hospital-acquired pneumonia [18] and was not enrolled. Repeated episodes of pneumonia in the same patient within a two-week period after enrolment were regarded as a single episode.

Data collection

Demographic and clinical data were collected through direct interviews of patients or their guardians and from reviews of medical charts and laboratory databases. Data on patient background, comorbid illnesses, risk factors for aspiration-associated pneumonia, symptoms, physical signs, laboratory and radiological results, therapeutic information, and outcomes were collected.

Definitions

HCAP was defined, based on the American Thoracic Society and Infectious Disease Society of America criteria, as pneumonia in any patient who met at least one of the following criteria: hospitalisation for 2days in the preceding 90days; residence in a nursing home or extended care facility; home infusion therapy; chronic dialysis within 30days; and home wound care [19]. We did not use the criterion of family member infection with a multidrug resistant pathogen because of the difficulty in obtaining this information through history-taking in the study setting. Home infusion therapy and home wound care were combined into a home care variable. Cases of pneumonia that did not meet the HCAP criteria were defined as CAP.

Underlying health conditions

We defined underlying health conditions as ageing-related or chronic conditions which patients had already had before they contracted pneumonia. Especially for elderly people, those conditions are practically difficult to remove or modify. Candidate conditions were selected a priori from those previously reported as mortality-associated factors [5, 8, 10, 20,21,22]: age; sex; HCAP conditions [hospitalization 2days in the preceding 90days, nursing home residency, home infusion therapy, chronic dialysis within 30days, and home wound care]; comorbid illnesses [congestive heart failure, liver disease, renal disease, neoplastic disease, chronic lung diseases, diabetes mellitus, and dementia]; risk factors for aspiration pneumonia [witnessed aspiration, chronically impaired conscious level, chronic neurologic disorders, tube feeding, and bed-ridden state]; and body mass index [BMI] [low:  30 per minute, and blood pressure [