M-protein assays
The disclosure provides methods for measuring M-proteins in a biological sample obtained from a subject, comprising applying purified immunoglobulins to a liquid chromatography (LC) mass spectrometry (MS). In some aspects, the immunoglobulins are purified using an immunocapture (IC). In certain aspects, the subject has a plasma cell disorder, e.g., multiple myeloma.
1 . A method of
measuring M-protein in a biological sample obtained from a subject having a plasma cell disorder, wherein the M-protein is measured by:
(1) purifying immunoglobulins and free light chains in the biological sample by immunocapture,
(2) dissociating the purified immunoglobulins, and
(3) applying the dissociated purified immunoglobulins and free light chains to a liquid chromatography-mass spectrometer (LC-MS);
wherein the biological sample is a blood sample or urine sample;
wherein the liquid chromatography (LC) employs (i) a mobile phase A, comprising water with 0.1% formic acid, and (ii) a mobile phase B, comprising 0.1% formic acid in acetonitrile; and
wherein the mass spectrometer (MS) employs a capillary voltage of about 4000 V to about 6000 V.
2 . The method of claim 1 , wherein the biological sample is a urine sample or a serum sample.
3 . The method of claim 1 , wherein the subject received a previous therapy to treat a plasma cell disorder.
4 . The method of claim 1 , wherein the M-protein comprises:
(i) an IgG, an IgA, and IgM, an IgD, a fragment thereof, or any combination thereof;
(ii) a kappa isotype or a lambda isotype;
(iii) one or more free light chain; or
(iv) any combination of (i) to (iii).
5 . The method of claim 1 , wherein the MS comprises:
(i) an electrospray (ESI) time-of-flight (TOF) MS;
(ii) a laser desorption ionization (MALDI) TOF;
(iii) a MALDI TOF MS; or
(iv) any combination of (i) to (iii).
6 . The method of claim 1 , wherein the immunocapture is an automated immunocapture.
7 . The method of claim 1 , wherein the purified immunoglobulins are dissociated by chemical reduction.
8 . The method of claim 1 , wherein:
(i) the LC is an ultra-performance (UC) LC, or
(ii) The LC is on-line with the MS.
9 . The method of claim 1 , wherein the plasma cell disorder comprises multiple myeloma.
10 . The method of claim 9 , wherein the multiple myeloma comprises:
(i) a light chain multiple myeloma,
(ii) a plasma cell leukemia, or
(iii) both (i) and (ii).
11 . The method of claim 10 , wherein the plasma cell leukemia comprises a primary plasma cell leukemia or a secondary plasma cell leukemia.