Comparison of lower limit of normal values with a fixed ratio assessed by spirometry in obstructive and restrictive lung diseases in Indian population

  • Manisha Mandal Department of Physiology, MGM Medical College and LSK Hospital, Kishanganj, Bihar, India
  • Arup Bandyopadhyay Department of Physiology, MGM Medical College and LSK Hospital, Kishanganj, Bihar, India.
  • Arunima Datta Department of Physiology, MGM Medical College and LSK Hospital, Kishanganj, Bihar, India.
  • Srila G Chowdhury Department of Physiology, MGM Medical College and LSK Hospital, Kishanganj, Bihar, India.
Keywords: Concordance, fixed‑ratio, lower limit of normal, obstructive, restrictive

Abstract

Background and Aim: Spirometric parameters are approximated by the normal distribution and using lower limit of normal (LLN) minimize the misclassification with fixed‑ratio protocol in interpretation of spirometry results. This study investigates prevalence and characterization of obstructive and restrictive lung function impairments, and dissimilarities between two guidelines interpreting spirometry. Methods: This study was conducted to assess the lung function in students and patients (n = 74) of MGM Medical College, Kishanganj, Bihar, between September 2012 and May 2014, using computerized Spirometer. Results: Forced vital capacity (FVC), forced expiratory volume in the 1st s (FEV1)/FVC, forced expiratory flow25–75% (FEF25-75%), peak expiratory flow rate (PEFR) were normally distributed with inflection at their mean ± standard deviation. FEF25–75%, and PEFR were higher in normal individuals compared to individuals with respiratory disease. FEV1/FVC were lower, and FVC were higher in obstructive disease while the reverse results were obtained in restrictive disease category. Restrictive disease by fixed‑ratio was found with 55% negative predictive value (NPV) and 5% positive predictive value (PPV), while the normal cases by fixed‑ratio criteria was found with 91% NPV and 15% PPV versus LLN criteria. There were 58 individuals with normal spirometries under the LLN method but a discrepant of only 12 fixed‑ratio normal results. Concordance analysis by kappa statistics yielded a κ = 0.017. Conclusion: Older adults are more pulmonary susceptible. The performance of LLN criteria in differentiating respiratory diseases is better than the fixed‑ratio criteria. Poor agreement exist between the fixed‑ratio and LLN protocols in interpreting spirometric results. There is the difference between the LLN and fixed‑ratio criteria which need to be redressed with population‑specific reference values.

Published
2015-01-31
How to Cite
Mandal, M., Bandyopadhyay, A., Datta, A., & Chowdhury, S. G. (2015). Comparison of lower limit of normal values with a fixed ratio assessed by spirometry in obstructive and restrictive lung diseases in Indian population. International Journal of Clinical and Experimental Physiology, 2(1), 66-72. Retrieved from https://ijcep.org/index.php/ijcep/article/view/49