SEASONAL TREND IN ONSET OF LUNG CANCER

Modeling Seasonal and Spatiotemporal Variation: The Example of Respiratory Prescribing

Many measures of chronic diseases, including respiratory disease, exhibit seasonal variation together with residual correlation between consecutive time periods and neighboring areas. We demonstrate a strategy for modeling data that exhibit both seasonal trend and spatiotemporal correlation, using an application to respiratory prescribing. We analyzed 55 months (2002-2006) of prescribing data from the northeast of England, in the United Kingdom. We estimated the seasonal pattern of prescribing by fitting a dynamic harmonic regression (DHR) model to salbutamol prescribing in relation to temperature. We compared the output of DHR models to static sinusoidal regression models. We used the DHR-fitted values as an offset in mixed-effects models that aimed to account for the remaining spatiotemporal variation in prescribing rates. As diagnostic checks, we assessed spatial and temporal correlation separately and jointly. Our application of a DHR model resulted in a better fit to the seasonal variation of prescribing than was obtained with a static model. After adjusting for the fitted values from the DHR model, we did not detect any remaining spatiotemporal correlation in the model's residuals. Using a DHR model and temperature data to account for the periodicity of prescribing proved to be an efficient way to capture its seasonal variation. The diagnostic procedures indicated that there was no need to model any remaining correlation explicitly.

Indications for performing flexible bronchoscopy: Trends over 34 years at a tertiary care hospital

BACKGROUND AND AIM

Due to its easy maneuverability, patient comfort and documented safety as an outpatient procedure, flexible bronchoscopy (FB) has replaced rigid bronchoscopy for routine diagnostic use. Herein, we report our 34-year experience with outpatient performance of FB.

MATERIALS AND METHODS

This was a retrospective analysis of all FB procedures performed between September 1979 and November 2013 (period I: 1979-1990; period II: 1991-2000; period III: 2001-2013) in a tertiary care hospital. Demographic profile of patients, indications for performing FB, and annual and seasonal trends were noted from the records.

RESULTS

A total of 24,814 bronchoscopies were performed during the study period. The mean (SD) age of patients (71.6% males) was 48.4 (15.5) years. The number of procedures performed per decade showed an absolute increase by 322%. The most common indication for FB was suspected bronchogenic carcinoma (32.2%) followed by pulmonary infections (18.6%) and interstitial lung diseases (13%). The proportion of annual cases due to interstitial lung diseases (3.9% in period I to 16.2% in period III) increased over the years, whereas disorders such as hemoptysis and pleural effusion showed a declining trend as an indication for FB. A seasonal trend was observed for diseases such as sarcoidosis, bronchogenic carcinoma and pulmonary infections. Six deaths were encountered during the study period in patients undergoing FB.

CONCLUSION

FB is increasingly being performed in the diagnosis of respiratory disorders and is a safe outpatient procedure. Although bronchogenic carcinoma remains a common indication for performing FB, benign conditions such as pulmonary infections and sarcoidosis constitute important indications in the Indian scenario.