On January 19, 2023, the National Intellectual Property Administration issued the Examination Decision on Invalidation Request No. 60416, deciding to maintain the validity of Chinese Invention Patent No. 200880121086.6 (invention title: "Method and Kit for Quantitative Determination of Small Dense LDL Cholesterol") whose patentee is Denka Co., Ltd., and rejecting the invalidation declaration request filed by the invalidation declarer against the patent for the method of determining small dense LDL cholesterol. Beijing Caihe Law Firm was entrusted by Denka Co., Ltd. to act as the agent of the patentee in the above-mentioned invalidation declaration request case. Key Points of This Case: The patent involved in the case, namely Chinese Invention Patent No. 200880121086.6 (also referred to as the "method patent"), and Chinese Invention Patent No. 201410058250.0 (also referred to as the "product patent") have a parent case and divisional case relationship. Prior to this, the product patent had undergone challenges from four patent invalidation declaration requests, and the final results were all maintaining its validity.