PT - JOURNAL ARTICLE AU - Michael S. Hofman AU - Nigel C. Smeeton AU - Sheila C. Rankin AU - Tom Nunan AU - Michael J. O'Doherty TI - Observer Variation in Interpreting <sup>18</sup>F-FDG PET/CT Findings for Lymphoma Staging AID - 10.2967/jnumed.109.064121 DP - 2009 Oct 01 TA - Journal of Nuclear Medicine PG - 1594--1597 VI - 50 IP - 10 4099 - http://jnm.snmjournals.org/content/50/10/1594.short 4100 - http://jnm.snmjournals.org/content/50/10/1594.full SO - J Nucl Med2009 Oct 01; 50 AB - Many studies demonstrate a high accuracy for PET in staging lymphoma, but few assess observer variation. This study quantified agreement for staging lymphoma with PET/CT. Methods: The PET/CT images of 100 patients with lymphoma who had been referred for staging were reviewed by 3 experienced observers, with 2 observers reviewing each series a second time. Ann Arbor stage and individual nodal and extranodal regions were assessed. Weighted κ (κw) and intraclass correlation coefficient were used to compare ratings. Results: Intra- and interobserver agreement was high for Ann Arbor stage (κw = 0.79–0.91), number of nodal regions involved (intraclass correlation coefficient, 0.83–0.93), and presence of extranodal disease (κ = 0.74–0.86). High agreement was also observed for all nodal regions (κw &gt; 0.60) except hilar (κw = 0.56–0.82) and infraclavicular (κw = 0.14–0.55). Lower agreement was observed for bowel involvement (κw = 0.37–0.71). Conclusion: Experienced observers had a high level of agreement using PET/CT for lymphoma staging, supporting its use as a robust noninvasive staging tool. Further research is needed to evaluate observer variability for restaging during and after chemotherapy.