Prognosis of primary care patients aged 80 years and older with lower respiratory tract infection

Patients and setting

Data from a large cohort of older patients with LRTI, used by Bont et al,22 were analysed. The data originated from the database of the Utrecht GP Research Network. In this network 35 GPs have been registering morbidity in electronic medical files of approximately 58 000 patients since approximately 1990. These patients are a reflection of the Dutch population with respect to age and sex. Contact data and diagnoses are registered according to a protocol using the International Classification of Primary Care (ICPC) codes and, when necessary, additional detailed definitions of diagnoses. Data were collected from January 1997 to February 2003. Patients aged ≥80 years at the time of LRTI diagnosis were selected and analysed.

Definition of LRTI and exclusion criteria

LRTI episodes were selected according to ICPC codes. Pneumonia (R81) was defined as evidence of pulmonary consolidation based on physical examination or chest X-ray; acute bronchitis (R78) was defined as coughing with diffuse abnormalities on pulmonary examination (wheezing and crepitations); and the definition of exacerbation of COPD (R91, R95) was based on the criteria of Anthonisen et al.23 Multiple episodes in the same patient were included provided there was at least a 3-week symptom-free interval.

Patients were excluded if they were treated with antibiotics within the previous 3 weeks for another respiratory problem. Other exclusion criteria were: lung or haematological malignancy, HIV infection or AIDS, using immunosuppressive medication, or hospitalisation during the 2 weeks prior to the diagnosis.

Potential predictors

The choice of potential predictors was based on relevant literature.7^–12^,14^–17^,21^,22^,24^–26 Age, sex, current use of medication, comorbidity, and healthcare use in the previous 12 months, including hospitalisation and GP visits, were regarded as potential predictors. Current use of medication was defined as medication prescribed on the day of diagnosis and ≥1 week prior to that day. Previous use of antibiotics was scored positive if the last tablet of a course was prescribed <1 month prior to diagnosis of LRTI. Comorbidity was scored using the ICPC codes in the patient record. The following illnesses were recorded: chronic bronchitis, COPD or emphysema (R91, R95), asthma (R96), malignancies (other than haematological or lung), congestive heart failure (K77, K82), myocardial infarction or other ischaemic heart diseases (K75, K76), angina pectoris (K74), stroke/cerebrovascular accident (K90), dementia (P70), neurological diseases including multiple sclerosis and Parkinson's disease (N86, N87, N99), diseases of the kidney and urinary tract (U99), diseases of the liver such as hepatitis and cirrhosis (D72, D97), and diabetes (T90).

Definition of the outcome

The combined outcome was defined as the occurrence of hospitalisation or death within 30 days after LRTI diagnosis, regardless of the primary cause. The outcome mortality was also analysed separately. Hospitalisation was regarded as an outcome if the patient stayed at least one night in the hospital.

Data analysis

Descriptive statistics and mean (standard deviation) were calculated in patients with or without the outcome. Multivariable logistic regression analysis was used to estimate the independent association between the combined clinical outcome and potential predictors. As many patients had more than one episode of LRTI and observations could be dependent, generalised estimating equations were used to adjust for within-person dependency.27 A univariable analysis was performed, and the variables found to have an association with the outcome (P≤0.2) were included in the multivariable analysis. Odd ratios and their 95% confidence intervals (CI) were estimated as approximation of the relative risk. Data analyses were performed using SPSS (version 15.0).

Summary of main findings

Five variables were identified that were independently associated with 30-day hospitalisation or death in primary care patients aged ≥80 years with a LRTI: type of LRTI, diabetes, the use of oral glucocorticoids, the use of antibiotics in the previous month, and hospitalisation in the previous year.

Strength and limitations of the study

This study has various strengths. First, data for the predictors were obtained from a large database that has been shown to be valid in many previous studies of respiratory infections.28^–30 The participating GPs are trained and register diagnoses according to a protocol using ICPC codes. Second, a relatively low number of predictive factors (five) were found that are readily available in the patients' files and can be routinely used in daily practice. A potential shortcoming is that it was not possible to validate the data in another cohort. It was also not possible to collect clinical data on patients' history or physical examination because of the retrospective study design. Other studies examining prognostic factors of pneumonia or LRTIs have identified several clinical predictor variables, such as confusion, respiratory rate, temperature, and blood pressure.7^,8^,11^–13^,16^,17^,24

Future studies should use a prospective design and also take clinical data into account. While these studies are not available yet, the authors believe that the present results are very useful for GPs. Regarding the endpoints, it should be noted that hospital admission is a marker of disease severity but also of social circumstances and subjective decisions. However, whatever the cause of the admission to hospital is, it is a very relevant endpoint for patients that it is important to anticipate.

Comparison with existing literature

The five predictors found were reported earlier in other populations. It has been shown that diabetes mellitus is associated with an increased susceptibility to infection,31^–33 and that patients with diabetes have an increased risk of complications when they have an LRTI.22^,31 The present results show that, in particular, patients with insulin-dependent diabetes mellitus had a greater risk for the combined outcome. The same is probably true for other chronic diseases. It was found that the use of oral glucocorticoids is a predictor for the outcome. This probably means that patients with severe COPD do have an elevated risk, while mild cases do not. The use of previous antibiotic is probably also an indicator of serious underlying disease, and the fact that this also predicted poor outcome supports the study's other findings.

It was remarkable that no clear association was found between heart failure and age with mortality and hospitalisation. Heart failure was very common in the study subgroup (33.4%). Presumably, many older persons have mild heart failure that overall does not clearly increase their risk for complications. However, it is well known that patients with severe cardiac failure have an unstable health condition and a high complication rate.34 It was not possible to distinguish between mild and severe cardiac failure. A few other studies on cardiac failure in patients with LRTI show conflicting results.18^,21^,22^,25

There is also discussion about age as a risk factor for complications.7^,9^,11^,12^,14^,17^,19^–22^,24^,26 In one of these studies it is suggested that age could lose specific weight as a prognostic factor for community-acquired pneumonia when including older patients only.11 Especially in the older population, age in itself could become less important, and other factors, most notably underlying diseases, could have more prognostic value.

Implications for clinical practice and future research

Serious comorbidity, especially insulin-dependent diabetes and serious COPD indicated by use of oral glucocorticoids, elevates the risk for complications in persons aged ≥80 years with LRTI. This risk is independent of age. The analysis in this study should be repeated in a validation cohort, and prospective studies should examine to what extent signs and symptoms could further improve risk assessment of patients aged ≥80 years with LRTI. In addition, intervention studies should assess to what extent the use of prognostic models like the present one would support management of these patients.