Obtaining spirometric reference values when height is not available - comparison of alternative anthropometric...

Area of Science:

• Pulmonary Function Testing
• Anthropometry
• Biostatistics

Background:

• Accurate height measurements are essential for establishing reference values in respiratory function tests like Forced Vital Capacity (FVC) and Forced Expiratory Volume in 1st second (FEV1).
• Height is not always available, necessitating alternative methods for estimation.
• Existing literature offers various formulas to estimate height for these clinical applications.

Purpose of the Study:

• To evaluate and compare different anthropometric methods for estimating height.
• To determine the most accurate method for predicting FVC and FEV1 reference values when true height is unavailable.

Main Methods:

• True stature (TS) and five alternative height estimations (arm span regression, arm span fixed correction factor (ASF), half arm span, knee height, ulnar length) were measured.
• Statistical analyses including T Student Test, Wilcoxon test, Intraclass Correlation Coefficient, and Bland-Altman plots were used to assess differences and agreement.
• Predicted FVC and FEV1 values derived from estimated heights were compared against those calculated using true stature.

Main Results:

• All tested anthropometric measures, except ASF, showed statistically significant differences compared to true stature for predicting FVC and FEV1.
• Wide limits of agreement were observed across all alternative height estimation methods.
• Overestimation of predicted FVC and FEV1 was noted with all methods except ASF.

Conclusions:

• Arm span with a fixed correction factor (ASF) is the most accurate and recommended method for estimating height to obtain predicted FVC and FEV1 values.
• Despite its accuracy, users should acknowledge the potential for a degree of error when using ASF.
• This finding supports the clinical utility of ASF in scenarios where true height is not obtainable for pulmonary function assessments.