Cardiothoracic Ratio (CTR) Among Patients Presenting for Chest X-ray in Radiology Department at Mulago National Referral Hospital: A Patients’ Health Indicator for Clinical Application.

Introduction/background: The heart is vital, and even minor dysfunctions can significantly impact the body. Cardiologists need always to determine heart size, which varies with physiological changes. Advanced measurement techniques are costly and often inaccessible to a common man. Measuring the cardiothoracic ratio (CTR) via conventional X-ray is a common and more affordable option, but there's a need for even cheaper alternatives Objective: To determine relationship between CTR and presenting clinical indications and to relate CTR to the body parameters to find an appropriate relationship that can be utilized in low resource facilities in determining heart size. Methodology: This cross-sectional study involved 386 patients undergoing chest radiographs at Mulago National Specialized Hospital's radiology department. Data were summarized using frequencies and percentages. Associations between the cardiothoracic ratio (CTR) and independent variables were analyzed using Pearson’s chi-square, Fisher’s exact test, Spearman’s correlation coefficient, simple linear regression, and multivariate regression. Statistical significance was set at a p-value of < 0.05. Results: The median cardiothoracic ratio (CTR) was 0.46, with an interquartile range of 0.42 to 0.50. Female patients had a higher CTR than males. Significant positive correlations were found between CTR; and BMI (p < 0.001, correlation 0.21), and BSA (p = 0.016, correlation 0.12), and BSI (p < 0.001, correlation 0.19). The diagnostic accuracy of a linear regression equation containing BSA as an estimator of CTR showed relatively fair performance compared to the linear regression equations with BSI and BMI. It showed sensitivity, specificity, and positive and negative predictive values of 29.2%, 86.0%, 63.6%, and 59.0% for males, and 8.3%, 98.1%, 75.0%, and 60.7% for females, respectively. Conclusion: BSA shows a moderately good relationship with CTR, while the influence of body habitus on CTR is minimal. Thus, using body parameters to predict CTR should be approached cautiously. We recommend conducting a similar study on a more diverse general population