In this video lecture, Dr. Yoshitaka Miyakawa discusses:
- The distinction between primary cold agglutinin disease and secondary cold agglutinin syndrome, including their differing pathophysiology and diagnostic criteria.
- Common laboratory and pre-analytical pitfalls in CAD diagnosis, particularly the importance of maintaining blood samples at 37°C to avoid false negative results.
- How serum studies, bone marrow histopathology, flow cytometry, and MYD88 mutation testing help confirm CAD and distinguish it from Waldenström macroglobulinemia and other lymphoproliferative disorders.
Dr. Yoshitaka Miyakawa is Professor of the Department of Hematology, Saitama Medical University, Saitama Japan. He brings extensive global experience across academia and industry, including prior research roles at Roche and as a postdoctoral fellow at the University of Washington. He has played a key role in clinical trials of innovative therapies across AIHA (wAIHA, CAD), ITP, TTP, aHUS, and gene therapy for hemophilia.
(Video Lecture Summary)
Introduction
Dr. Yoshitaka Miyakawa presents a concise approach to the precision diagnosis of cold agglutinin disease (CAD), with a particular emphasis on laboratory interpretation and diagnostic pitfalls. He begins by distinguishing primary CAD from secondary cold agglutinin syndrome and outlines the core laboratory features required for diagnosis.
Primary CAD vs. Secondary Cold Agglutinin Syndrome
Dr. Miyakawa describes primary CAD as a distinct clonal B-cell disorder classified as a monoclonal gammopathy of clinical significance (MGCS). In CAD, clonal bone marrow B cells produce a monoclonal IgM kappa antibody directed against the I antigen on red blood cells.
In contrast, secondary cold agglutinin syndrome represents a reactive hemolytic process associated with infections such as mycoplasma, Epstein-Barr virus, and COVID-19, as well as autoimmune disease and overt B-cell malignancies.
He emphasizes that diagnosis of primary CAD requires evidence of chronic hemolysis, a monospecific direct antiglobulin test strongly positive for C3d and typically negative for IgG, a significant cold agglutinin titer, and exclusion of underlying infection or malignancy.
The 37°C Pre-Analytical Pitfall
A major focus of the lecture is the importance of proper specimen handling. Dr. Miyakawa highlights what he describes as the “37-degree pre-analytical pitfall.” If blood samples cool to room temperature before plasma or serum separation, cold agglutinins may rapidly bind to red blood cells through autoabsorption.
This can lead to falsely low or negative cold agglutinin titers and failure to detect monoclonal IgM bands on serum studies. To avoid this issue, samples should be maintained at 37°C from blood draw through plasma or serum separation.
Confirmatory Laboratory Studies
Dr. Miyakawa reviews the additional studies used to confirm the underlying clonal B-cell process in CAD. Serum protein electrophoresis and immunofixation commonly reveal a monoclonal IgM kappa spike, though proper warm handling is again essential for accurate detection.
Bone marrow flow cytometry typically demonstrates kappa light-chain restriction among CD19- or CD20-positive B cells, often with a kappa-to-lambda ratio greater than 3.5. Low complement C4 levels may also be observed due to classical complement pathway consumption.
Bone Marrow Histopathology
The lecture also addresses the challenges of bone marrow interpretation in CAD. Dr. Miyakawa explains that the characteristic sparse intertrabecular B-cell infiltrates may be obscured on routine H&E staining by compensatory erythroid hyperplasia.
However, targeted immunostaining can better identify nodular and diffuse mature B-cell populations expressing CD19, CD20, and PAX5, accompanied by scattered IgM-positive plasma cells.
He additionally highlights the importance of expert hematopathology review, noting that decentralized pathology evaluation may misclassify CAD as reactive lymphocytosis or other low-grade lymphomas. Centralized expert review substantially improves diagnostic accuracy and reduces misclassification.
MYD88 Mutation Testing and Molecular Features
Dr. Miyakawa emphasizes the value of MYD88 L265P mutation analysis in difficult diagnostic cases. While Waldenström macroglobulinemia and lymphoplasmacytic lymphoma are typically MYD88-positive, primary CAD is generally MYD88-negative. Detection of the mutation therefore argues against primary CAD.
He also reviews several molecular and cytogenetic features associated with CAD, including frequent IGHV4-34 gene usage, recurrent somatic mutations such as KMT2D and CARD11, and cytogenetic abnormalities including trisomy 3 combined with trisomy 12 or trisomy 18.
Diagnostic Algorithm and Conclusion
Dr. Miyakawa concludes by presenting a practical five-step diagnostic algorithm for CAD:
- Confirm hemolysis with LDH, bilirubin, and haptoglobin.
- Perform a monospecific DAT demonstrating C3d positivity and IgG negativity.
- Confirm a significant cold agglutinin titer.
- Distinguish secondary cold agglutinin syndrome from primary CAD by evaluating for underlying disorders.
- Confirm primary CAD using serum protein electrophoresis, bone marrow biopsy, and flow cytometry.
He closes by emphasizing that a structured and methodical diagnostic approach can help clinicians avoid common laboratory pitfalls and improve diagnostic accuracy in CAD.