<prompt> A lady presents with right knee swelling.Aspiration was done in which CPPD crystals were obtained.Next best investigation isANARFCPKTSH  <response>: Secondary CPPD deposition is associated with hypothyroid,hence TSH level should be assessed. Other conditions: Hyperparathyroidism Hemochromatosis Hypophosphaemia Hypomagnesemia Diabetes 