Discussion
We report that among patients discharged from hospital following admission with CAP, a quarter were readmitted within 30 days of whom two-thirds were readmitted within 14 days of discharge. The likelihood of readmission was associated with the presence of underlying comorbidity with the highest OR for readmission associated with diabetes (with complications), cancer and CKD.
Others have investigated the rates and predictors of readmission following CAP.9 10 The Pneumonia Patient Outcomes Research Team Study reported that among 1343 US patients, the 30-day rehospitalisation rate following CAP was 10.1%,9 while a subsequent US study examining 45 134 patients recruited between 2001 and 2007 reported a 30-day hospitalisation rate following CAP of 13.2%.10 One explanation for the higher readmission rates reported in our study may be the proportion of the patients with multiple comorbidities. The link between comorbidity and readmission has been demonstrated in a number of prior studies.11–13 A study of patients aged >65 years recruited from 20 hospitals, covering 70% of the Spanish population, showed a 30-day readmission rate following CAP of 11.39%.12 In that study, 91% of those who were readmitted had comorbidities, particularly chronic respiratory failure, heart failure and chronic liver disease, reflecting our finding that chronic organ failure predicts readmission. In a US study charting 1 168 624 hospitalisations due to CAP over a 2-year period, the 30-day readmission rate was 18.3% and 22% of those readmissions were due to pneumonia which is comparable with the 24% of readmissions due to pneumonia in our study.11 In a US study of 7 hospitals following up 577 patients discharged with CAP, 12% were readmitted within 30 days with the authors reporting that 74% of readmissions were comorbidity related.13 However, in the UK, Daniel et al conducted a study of 108 working-aged patients with CAP who were recruited from four hospitals.14 They showed 4.6% were readmitted within 4 weeks of discharge and found no single factor to be predictive of healthcare reconsultation post-discharge. The key differences between that cohort and the patients presented here are age and the burden of comorbidity. We found that age alone was not predictive of readmission and our cohort (median age 73 years) had an average CCI of 9.5, whereas Daniel et al described a cohort of median age 50 years with median CCI of 0. A systematic review by Weinreich et al revealed a median 30-day readmission rate of 17.3% following hospitalisation. The authors concluded that, similar to our findings, the majority of readmissions were related to the impact of pneumonia on comorbidities.15 Another systematic review reported a 30-day readmission rate of 12%–20% and highlighted the importance of cardiovascular and respiratory comorbidity as the readmission diagnosis and also reported that pneumonia itself accounted for 22%–29% of readmission diagnoses.16 These data support our findings and support the hypothesis that pneumonia exacerbates frailty, leads to decompensation of underlying organ failure and that these factors provoke readmission.
Our study demonstrated that two-thirds of readmissions occurred within the first 2 weeks following discharge with 41% occurring within 7 days. In a US study analysing claims-based data from over 1 million hospitalisations due to pneumonia, Dharmarajan et al reported that, consistent with our findings, 62.6% of these readmissions occurred during days 0–15 following discharge with a median time to readmission being 12 days.11 A cohort study of 3996 subjects hospitalised with CAP in Sydney, Australia reported a readmission rate of 14.1% with a median time to readmission being 7 days with CAP responsible for 17.8% of all readmissions.17 The authors reported a relationship between 30-day readmission and factors such as comorbidity, LOS and prior healthcare utilisation in the form of an index. In an earlier study of 270 patients hospitalised with CAP, a 30-day readmission rate of 23% was observed with readmission predicted by the Yale New Haven Readmission Risk Score which included certain comorbidity such as diabetes mellitus and congestive cardiac failure.18 While a convincing argument already exists for inpatient respiratory specialist review of those with CAP, our data support a more holistic approach to CAP care if readmissions are to be reduced.19 20 It may be that the ideal inpatient pathway for CAP includes respiratory specialist review during the acute phase of the admission followed by a multidisciplinary assessment later in the admission, incorporating identification and optimisation of comorbidities. The strong association observed in our study between metastatic cancer and early readmission would support an increased emphasis on community palliative care liaison, advanced care planning and a greater emphasis on review of social circumstances during discharge planning following CAP. To reduce readmission, in addition to a targeted focus on comorbidities, multidisciplinary pre-discharge evaluation should identify candidates for intermediate care along with directing the implementation of specific interventions for optimising mobility, reducing frailty and addressing social circumstances. With two-thirds of readmissions occurring within 14 days of discharge, intermediate care and supported discharge schemes are likely to be more successful than early outpatient clinic follow-up, but further studies are required to determine the effectiveness of implementing such pathways.21
A strength of this study lies in the accuracy of the diagnosis of CAP. AQ is a nationally recognised quality improvement initiative in the UK where data entry is strictly monitored and data quality audited. Furthermore, as described earlier, the diagnosis of CAP for entry into the AQ Programme is robust as opposed to simply labelling the patient with a diagnosis of CAP based on coding alone. However, certain limitations exist in our study. Our analysis did not measure an index of frailty in the study population nor did our study record details of social circumstances including nursing home residential status (although surrogates of comorbidity) or a history of cigarette smoking which may have been relevant in predicting readmission.10 22–25 Our analysis was limited in focusing on emergency hospital readmission rates which represent only one aspect of healthcare utilisation. Interestingly, while the overall hospital readmission rate was low in the study by Daniel et al, some form of healthcare utilisation was noted in 66% of the cohort in the 4-week period post-hospital discharge with just over 90% of these being general practice consultations.14 It is possible that these differences in hospital versus primary care consultation represent regional differences in healthcare provision. The northwest of the UK has the highest rates of socioeconomic deprivation in the country and relatively poor access to primary care in comparison with other areas and this may account for the apparent differences in how patients access healthcare.26 Furthermore, our analysis did not take into account the effects of medications on readmission rate, for example, recording a history of oral corticosteroid use and the cardiovascular drug count, both of which have been associated with readmission, and this effect would have been useful to measure in our cohort.10 In terms of the index admission, our dataset did not measure the time to clinical stability which has been shown to be predictive of 30-day outcomes nor did our study take into account differences in terms of microbiological aetiology.27 28