Validity of Prediction of Thoracic Gas Volume and Body Composition UsingAir Displacement Plethysmography in People Living with HIV in SouthwestEthiopia

Background: Body composition assessment has become increasingly popular in clinical and research areas. But any body composition measurement technique that is used in both clinical and research settings should be reliable and valid. Objectives: Our first aim was to compare predicted thoracic gas volume (Vtgpred) with measured thoracic gas volume (Vtgmeas) using the BOD POD in people living with HIV/AIDS (PLWHA) in Southwest Ethiopia. The second aim was to determine the effect of thoracic gas volume (Vtg) measurement ways on estimation of body fat (BF) using the BOD POD in PLWHA in Southwest Ethiopia. Method: Cross-sectional study was conducted on 68 PLWHA who had follow up at Jimma University Specialized Hospital (JUSH). Subjects were collected using convenience sampling technique. Agreement between the methods was tested using paired t-test, Pearson’s correlation, linear regression, and Bland-Altman plot. Result: Much percent of study subjects were malnourished (60.3%). Vtg and percent body fat (%BF) did not differ significantly (p>0.05) between the two modes of assessment (predicted and measured). Strong correlation was observed between Vtgpred and Vtgmeas (r=0.82, p<0.001). Correlation between predicted %BF (%BFpred) and measured %BF (%BFmeas) was also strong(r=0.92, p<0.001). The regression of Vtgmeas(Y) against Vtgpred (X) (Y=- 0.369+1.140X, R2=0.68, SEE=0.015) did not significantly deviated from the line of identity. Similarly, the regression of %BFmeas (Y) against %BFpred (X=1·70+0.94X, R2=0·96) did not significantly deviated from the line of identity. Bland- Altman plot of the differences against the mean of Vtgpred and Vtgmeas and the differences against the mean of %BFpred and %BFmeas showed no systematic differences. Conclusion: The BOD-POD is a reliable technique to predict Vtg and body composition in PLWHA in Southwest Ethiopia. Therefore, researchers and clinicians can confidently use the predicted Vtg and body fat in place of the measured ones in PLWHA in Southwest Ethiopia.