Comparison of quantitative analysis to qualitative analysis for interpretation of lower limb lymphoscintigraphy
Date of Award
Master of Medicine (MMed)
Dr. Khalid Makhdomi
Prof. Zul Premji
Imaging and Diagnostic Radiology (East Africa)
Background: Lymphoscintigraphy is now the primary imaging modality used in determining a diagnosis in patients with suspected extremity lymphedema. However, analysis is mainly by visual qualitative analysis which is subjective and has a wide inter-observer variability. Subtle differences in ilioinguinal uptake between normal and abnormal limbs may be missed with visual qualitative analysis. This study seeks to compare quantitative analysis to qualitative analysis by computing percentage ilioinguinal nodes uptake at 1.5 hours.
Objectives: To compare quantitative analysis to qualitative analysis of lower limb lymphoscintigraphy in the diagnosis of lymphedema.
To determine the diagnostic accuracy of quantitative lymphoscintigraphy analysis.
Methodology: 52 lymphoscintigrams of consecutive patients meeting the study criteria were analyzed quantitatively. 53 normal and 51 abnormal limbs were analyzed. For both the normal and abnormal limbs, a region of interest was drawn around the injection site (B) and ilioinguinal nodes (A) at 1.5 hr. static images and the counts in these ROIs recorded. Percentage ilioinguinal nodes uptake was computed as: Analysis of variance was done to determine whether there is significant difference in ilioinguinal uptake between normal and abnormal limbs. Using different cut-offs, and qualitative analysis as a reference standard, specificity and sensitivity was calculated and the figures used to plot a receiver operator characteristics (ROC) curve. Area under the curve was estimated.
Findings: 52 patients; 36 females and 16 males (104 limbs) were analyzed. Proportion of male limbs with a lymphoscintigraphy proven lymphedema was significantly higher (78% vs 36%, p<0.001).
ANOVA revealed a statistically significant difference between the mean uptake of normal (19.7%) and abnormal limbs (5.5%) (F=81, p
Discussion: The statistically significant difference in the means of ilioinguinal uptake between normal limbs and limbs with lymphedema is indicative of reduced lymphatic function as seen in previous studies. More female subjects were enrolled in the study suggesting that edema of whatever etiology is more common in females. The higher proportion of male limbs with lymphedema indicates that edema in our male subjects was more likely to be due to lymphedema.
Nganga, E. C. (2015). Comparison of quantitative analysis to qualitative analysis for interpretation of lower limb lymphoscintigraphy (Unpublished master's dissertation). Aga Khan University, East Africa.
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