LYMPHOSCORE (Lymphoscintigraphy Scoring Reliability) Reliability of a New Qualitative and Semiquantitative Lymphoscintigraphy Scoring System for Primary Lymphedema

Primary lymphedema (PLE) is a rare chronic disorder. Extremity lymphoscintigraphy offers access for dynamic and functional information on peripheral lymphatics and lymph nodes. We aimed to assess intraobserver and interobserver reliability of a new lymphoscintigraphy quantitative and qualitative scoring system in a homogeneous population of adult patients followed for PLE of the lower limb(s). This is a monocentric retrospective study. Clinical files of patients who underwent a lymphoscintigraphy were reviewed for inclusion. Lymphoscintigraphies were interpreted twice by 2 observers with a washout period. To assess intraobserver and interobserver reliability for both lower limbs, Cohen κ and Gwet's AC1 reliability coefficients were calculated with 95% confidence interval and P value of the zero-reliability comparison test. To interpret reliability coefficients, we used the orders of magnitude reported by Landis and Koch. One hundred forty-four patients (288 limbs) with PLE were included. For intraobserver reliability, agreement range was 0.87-1 with an almost perfect agreement in all staging items of the score for both limbs with the lower limit of the 95% confidence interval ≥80%. Interobserver reliability was overall strong or almost perfect, ranging from 0.67 to 0.97. This new scoring system demonstrated excellent intraobserver reliability and a very good interobserver reliability. Lymphoscintigraphy, when performed in a referral center and interpreted by trained nuclear medicine physicians, is a reliable means of investigation in patients with PLE of the lower limbs. This reproducibility advocates for further use of lymphoscintigraphy in multicentric cohorts of PLE patients.