|Test||What Does it Detect?||Most Sensitive Test for:||Normal Range|
|SPIE†||Clonal immunoglobulin and/or clonal light chain||Confirming clonal immunoglobulin production||No M-spike present|
|UPIE†||Clonal immunoglobulin and/or clonal light chain||Confirming clonal light chain production||No M-spike present|
|Serum free light chain assay||Ratio of serum kappa:lambda light chains||Detecting low-level clonal light chain production; clonality assumed if ratio is far from 1:1||Kappa:lambda ratio = 0.26–1.65‡|
AL = light-chain; ATTR = transthyretin amyloidosis; SPIE = serum protein electrophoresis with immunofixation; UPIE = urine protein electrophoresis with immunofixation.
↵∗ If any of these tests are abnormal, bone scintigraphy should not be used to make the diagnosis of ATTR amyloidosis, and biopsy is recommended.
↵† SPIE and UPIE are more sensitive than protein electrophoresis without immunofixation and should be ordered as the preferred tests.
↵‡ In patients with kidney disease, mild elevations in the kappa:lambda ratio are frequently encountered. In the setting of a normal SPIE/UPIE, a kappa:lambda ratio up to 2.5 can typically be considered normal.