Prediction Equation for Spirometric Parameters in Cairo Governorate Adult Population

Abstract

Context: Spirometry is the most common one used in assessing, diagnosing, and managing patients with different lung diseases. Prediction equations developed in one set of the population may not apply to a different set of populations.

Aim: This work aimed to develop prediction equations for spirometry pulmonary function parameters in a sample of the adult Egyptian population in the Cairo governorate. The secondary aim was to compare our derived equations of pulmonary function with international reference figures used in our spirometric lab facilities.

Methods: This observational cross-sectional population-based study was carried out at Embaba Chest Hospital upon 610 normal healthy subjects, aged between 20 - 45 years old. All subjects were subjected to history, clinical examination, and pulmonary function tests. These subjects were randomly selected in a cluster from registration records in different official health care facilities or community health centers. Subjects from records were invited by calling through land phone, cell phone, or e-mails. This study compared the international reference figures of mean predicted spirometry values with our derived predicted values of lung function parameters.

Results: The predicted equations for FEV1 were [(3.429+(-0.028*Age)+(-0.017*weight)+(0.018*height)], and [1.238+(-0.005*Age)+(-0.006*weight)+(0.014*height)] for males and females respectively. The predicted equations for FVC were [4.556+(-0.016*Age)+(-0.012*weight)+(0.01*height)], and [2.494+(-0.009*Age)+(-0.005*weight)+(0.0100*height)] for males and females respectively. It was found that the Egyptian predicted mean values were within the lower limit of normal LLN and upper limit normal ULN when each of these prediction equations was used.  These results were higher than US population with regards to FEV1 4.089(0.498) Vs 3.88(0.04) [p<0.001] in males, but non-significant in females 2.865 (0.171) Vs2.85 (0.33) [p0.449]. FVC was found statistically higher in Egyptian population in female gender 3.513(0.164) Vs 3.36(0.33) [p<0.001] and non-significant difference in males 4.743(0.31) Vs 4.74(0.36) [p0.932] compared to US population. Besides, there were considerable differences between Omani and Jordanian populations and Egyptian populations, on the other hand regarding FEV1 and FEF _25-75% in the male gender.

Conclusion: The Linear regression equations had a direct linear correlation with height and inverse linear correlation with age. The implemented reference values utilized in our lab's facilities are particularly suited with the present study’s derived predicted lung function equation. In addition, equations had diverse determination coefficients from those reported by authors in adult Omani and Jordanian populations.