Protein Electrophoresis in Clinical Diagnosis PDF

Preface

This text presents the use of protein electrophoresis of serum, urine, and cerebrospinal fluid in clinical diagnosis. It is a revision of two previous books on this subject with several substantive and many trivial changes. The title has been changed from High-Resolution Electrophoresis and Immunofixation: Techniques and Interpretations to the present one in recognition of the fact that the information in this book may be useful to individuals who interpret a wide variety of electrophoretic gels (high-resolution or not).

There have been several significant changes in the field since the second edition of High-Resolution Electrophoresis and Immunofixation: Techniques and Interpretation was published in 1994 by Butterworth-Heinemann. That text was largely written in 1993, making it 10 years old at the time of publication of this book. At the time the second edition was written there was no high-resolution technique available that provided automated or semi-automated methods for laboratories with a large clinical volume of testing. There are now several products presented, with examples. Some of them are gel-based, others use capillary zone electrophoresis. Some automated gel-based systems have achieved an excellent degree of resolution that allows efficient performance of high-quality techniques by even moderately sized institutions. At the time of the second edition, capillary zone electrophoresis itself was quite new with no methods available that had been approved for use in the clinical laboratory by the Food and Drug Administration. I discussed it only briefly. Now two such instruments are already in place in many laboratories and there have been several publications about the advantages, artifacts and limitations of these techniques. Improved resolution especially of protein bands has resulted in better detection of bisalbuminemia by laboratories using capillary zone electrophoresis. That technique also has enhanced our ability to detect genetic variants such as α1-antitrypsin inhibitor deficiencies (PiZZ and PiSZ) as well as benign variants.

In addition to technical advances in the general detection and quantification of specific proteins, the techniques available to identify the monoclonal proteins have also changed significantly. Immunosubtraction using capillary zone electrophoresis was not even mentioned in the second edition. Now, immunosubtraction by automated technology is used in many laboratories that employ capillary zone electrophoresis. It is highly efficient, but suffers from a lack of sensitivity and flexibility when compared with immunofixation. This is discussed in the present text. For laboratories using some of the newer semi-automated gel-based techniques, semi-automated immunofixation is now available. Beyond the instruments, there are new reagents available such as the ‘Penta' (pentavalent) reagent that one company supplies as a potential screen for monoclonal proteins. Immunoselection was also just touched on in the second edition. Now that g heavy chain disease is more readily recognized, a broader discussion of immunoselection is provided. Advances have also been made in reagents available for measurement of monoclonal free light chains by nephelometry in both serum and urine. Recent publications indicate that measurement of free light chains in serum may be useful not only to follow patients with known monoclonal free light chains (Bence Jones proteins), but also to assist in the difficult diagnoses of amyloid (AL) and even non-secretory myeloma. This is discussed in Chapters 6 and 7.

In the second edition, high-resolution agarose gels were preferred for detecting oligoclonal bands in the cerebrospinal fluid from patients whose differential diagnosis included multiple sclerosis. Now, the recommendation is the use of isoelectric focusing or an immunofixation technique to identify the bands as immunoglobulins. One company currently offers a semi-automated immunofixation method for detecting oligoclonal bands (O-bands) in cerebrospinal fluid on unconcentrated fluid. There have also been improvements in the detection of leakage of cerebrospinal fluid into nasal and aural fluids; these are discussed in Chapter 8.

Beyond technical issues, there have been improvements in our knowledge of proper utilization and interpretation of protein electrophoresis when searching for the presence of a monoclonal gammopathy. In 1998, the College of American Pathologists Conference XXXII convened a panel of experts to provide recommendations for the clinical and laboratory evaluation of patients suspected of having a monoclonal gammopathy. These guidelines were published in 1999 and provide an important framework that emphasizes the partnership of clinicians with laboratory workers.

Urine evaluation has improved with the newer technologies and has been complicated by some current procedures. For example, individuals receiving a pancreas transplant may have the exocrine pancreas drainage empty into the urinary bladder. As discussed in Chapter 7, this results in gmigrating bands that may be mistaken for monoclonal gammopathies. They are exocrine pancreas secretions.

The method I suggested in the first edition and expanded in the second for tailored reporting with detailed sign-outs has been improved by feedback from our clinicians. Our current sign-outs are presented in tabular form and readers are encouraged to use them if they wish.

A couple of concepts were removed from this edition. The technique of two-dimensional electrophoresis, while useful in research has not caught on in the clinical laboratory and is not discussed in this volume. Further, the indirect immunofluorescence techniques reviewed in the previous texts has been replaced by immunohistochemical and flow cytometry studies.

Finally, in this text I recommend the use of the term monoclonal free light chain (MFLC) to replace the term Bence Jones proteins. It is both a practical and a technical improvement. Some individuals confuse the presence of an intact immunoglobulin monoclonal gammopathy in the urine with a Bence Jones protein. It is not. Bence Jones protein is a monoclonal free light chain and has much greater significance to the patient's diagnosis and prognosis than an intact immunoglobulin monoclonal gammopathy in the urine. The term MFLC says exactly what we found (i.e. a monoclonal free light chain). So it is technically correct and removes any possible ambiguity. This has the advantage that individuals will no longer use a hyphen that Dr Henry Bence Jones never used on any of the papers or books that he wrote.

I hope you enjoy this book, or at least find it useful. Your comments and questions help to provide a focus for making this text more relevant to the use of electrophoresis in clinical diagnosis. Please feel free to contact me via e-mail: [email protected].