Comparison of quantitative analysis to qualitative analysis for interpretation of lower-limb lymphoscintigraphy

Qualitative analysis of lymphoscintigrams is subject to wide variability and may miss subtle differences in ilioinguinal uptake between normal and abnormal limbs. This study compared quantitative analysis to qualitative analysis of lower-limb lymphoscintigraphy in diagnosing lymphedema. Fifty-two lymphoscintigrams performed using standardized protocol, 99-metastable technetium nanocolloid intradermal injection at the first interdigital space, were analyzed quantitatively. Fifty-three normal and 51 abnormal limbs were analyzed. For each limb, a region of interest (ROI) was drawn around the injection site, and ilioinguinal nodes on the 1.5 h static images and the counts in these ROIs were recorded. Percentage ilioinguinal nodes uptake was then computed. Analysis of variance (ANOVA) was performed to determine the difference in ilioinguinal uptake between normal and abnormal limbs. Specificity and sensitivity were calculated and the figures were used to plot a receiver operator characteristic (ROC) curve. Thirty-six females and 16 males (104 limbs) were analyzed. ANOVA revealed a significant difference between the mean uptake in normal (19.7%) and abnormal limbs (5.5%) (F = 81, P < 0.001). ROC had a maximal area under the curve of 0.924 (P < 0.001). The significant difference in the means of ilioinguinal uptake between normal and lymphedema limbs infers reduced lymphatic function. Ilioinguinal lymph node uptake is thus a reliable parameter in quantitative analysis of lymphoscintigrams.