{"entity":{"id":"cd38-expression","kind":"biomarker","name":"CD38 expression","aka":["CD38","CD38-positive","CD38 expression myeloma"],"tldr":"CD38 is on almost every myeloma cell, so daratumumab and isatuximab are given without testing for it. The stain matters afterwards: CD38 falls after treatment and can confuse flow cytometry and blood typing.","summary":"Daratumumab and isatuximab are CD38-directed antibodies labelled for multiple myeloma by line of therapy, not by CD38 level; every label describes the antigen only in the mechanism section. CD38 expression is near-universal on plasma cells and drops for months after anti-CD38 therapy, which is why laboratories use alternative gating in flow cytometry and why the drugs interfere with indirect antiglobulin tests.","asOf":"2026-09-23","links":[{"label":"DARZALEX prescribing information (DailyMed)","url":"https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a4d0efe9-5e54-467e-9eb4-56fa7d53b60b"}],"tags":["biomarker","surface-antigen","no-threshold"],"related":["bcma-expression","gprc5d-expression"],"cancers":["multiple-myeloma","myeloma-transplant-eligible","myeloma-transplant-ineligible","myeloma-relapsed-refractory"],"sections":[],"technologies":[],"targets":[],"drugs":["daratumumab","isatuximab"],"companies":[],"institutions":[],"pathways":[],"terms":["flow-cytometry"],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"target":"cd38","measurement":"ihc-score","scoringRule":{"text":"The label names the antigen in the drug's description but does not require it to be measured before treatment; no approval threshold exists for this readout.","quote":"DARZALEX is a CD38-directed cytolytic antibody","source":"https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a4d0efe9-5e54-467e-9eb4-56fa7d53b60b","sourceLabel":"DARZALEX prescribing information (DailyMed)"},"thresholds":[],"tests":[],"assays":[],"companionDiagnostics":[],"forPatient":"You will not usually be tested for CD38 before daratumumab or isatuximab; the antigen is present on virtually all myeloma cells. Tell any hospital laboratory you are on an anti-CD38 antibody, because it interferes with blood-matching tests for transfusion."},"route":"/biomarkers/cd38-expression/","neighbours":{"biomarker":[{"id":"bcma-expression","kind":"biomarker","name":"BCMA expression","route":"/biomarkers/bcma-expression/"},{"id":"gprc5d-expression","kind":"biomarker","name":"GPRC5D expression","route":"/biomarkers/gprc5d-expression/"}],"cancer":[{"id":"multiple-myeloma","kind":"cancer","name":"Multiple myeloma","route":"/cancers/multiple-myeloma/"},{"id":"myeloma-transplant-eligible","kind":"cancer","name":"Newly diagnosed multiple myeloma, transplant-eligible","route":"/cancers/myeloma-transplant-eligible/"},{"id":"myeloma-transplant-ineligible","kind":"cancer","name":"Newly diagnosed multiple myeloma, transplant-ineligible","route":"/cancers/myeloma-transplant-ineligible/"},{"id":"myeloma-relapsed-refractory","kind":"cancer","name":"Relapsed or refractory multiple myeloma","route":"/cancers/myeloma-relapsed-refractory/"}],"drug":[{"id":"daratumumab","kind":"drug","name":"Daratumumab","route":"/drugs/daratumumab/"},{"id":"isatuximab","kind":"drug","name":"Isatuximab","route":"/drugs/isatuximab/"}],"term":[{"id":"flow-cytometry","kind":"term","name":"Flow cytometry (immunophenotyping)","route":"/terms/flow-cytometry/"}],"target":[{"id":"cd38","kind":"target","name":"CD38","route":"/targets/cd38/"}]}}