OBJECTIVES: An accurate diagnosis is critical for determining prognosis and treatment options for patients with PTCL. However, the accurate diagnosis of PTCL remains challenging. Previous analyses have reported variable revision rates as high as 24%. However, the rate of revision among PTCL cases has not been characterized utilizing a large US claims database. METHODS: A retrospective analysis identifying newly diagnosed PTCL cases via ICD-9 and ICD-10 codes between 01/01/2010 - 12/31/2015 was conducted using the Truven MarketScan databases. Two PTCL claims during the study period were used to identify cases. Cases were indexed by the Date of first PTCL claim. Cases were required to have 6 months of pre-index baseline continuous enrollment and at least 6 months of post-index continuous enrollment. Cases with at least one prior claim for Hodgkin Lymphoma, DLBCL, EMZL or unspecified, uncertain and benign neoplasms at any time in the pre-index period were considered a case with diagnostic revision. The number of claims to confirm PTCL was changed from 2 to 1 to test the impact on the observed revision rate. RESULTS: A total of 289 cases with PTCL diagnosis were identified of whom 166 cases were without a diagnostic revision. There were 123 cases that had a diagnostic revision resulting in a diagnostic revision rate of 42.56%. The sensitivity analysis with a single PTCL claim required for inclusion resulted in a reduction of the revision rate to 33.56%. The median time to PTCL diagnosis in the commercial and Medicare populations was 154 and 219 days from misdiagnosis claim, respectively. CONCLUSIONS: This study found that diagnostic revision rates of PTCL ranges from 34% to 43%, highlighting the need for more accurate diagnostic testing to reduce unnecessary clinical burden associated with PTCL. Additional clinical data are required to understand how diagnostic revision impacts PTCL patient outcomes.