Diagnostic tests that are run by the doctor.
The basic peripheral blood count usually demonstrates an anaemia and the erythrocyte sedimentation rate (ESR – a basic test of active disease ongoing in the body) is usually very elevated due to the coating of the erythrocytes (red cells) with immunoglobulin. An immunoglobulin electrophoresis performed on the blood serum gives a characteristic picture in most cases: there is a very high spike on the electrophoretic strip indicating an over-expression in the serum of one protein type – which is, of course, the immunoglobulin that the malignant clone of cells makes – and often a suppression (immune paresis) of the other immunoglobulins.
The abnormal immunoglobulin is referred to as the abnormal paraprotein and the level of this paraprotein can and will be quantified by the doctor; serial measurements of this level assists the monitoring of the disease.
The immunoglobulin molecules are made up of two component heavy chains of peptides and two light chains; in myeloma, there is an overproduction and mismatch of light chain and heavy chain synthesis and an excess of the light chains, which are of sufficiently low molecular weight that they pass through the kidneys unimpeded and appear in the urine. They are detectable in the urine by a relatively simple test, and this test for such proteins is called the Bence-Jones protein test after the man who observed it first; a positive test is almost pathognomonic/diagnostic for myeloma.
A skeletal survey refers to the x-raying of all the skeleton to look for bony lesions and is performed in the work up of all myeloma cases; interestingly, the bone scans under-read the situation in myeloma. In a typical case, there are multiple lytic (i.e. black on x-ray) lesions in bone and where the skull which is very typically involved heavily has multiple holes in it on lateral skull x-ray, the term ‘pepper pot skull’ is used in the medical profession, as the skull appears with the rounded holes, such as is seen in the top of a pepper pot. These are truly multiple plasmacytomata.
The last and most important test is the bone marrow examination. For example, where there is only one painful bony l;esion and biopsy suggests a solitary plasmacytoma, then the discovery of abnormal/malignant plasma cells on the bone marrow proves for sure that the diagnosis is that of mutiple myeloma.
It should be noted that routine scanning of internal organs such as abdominal contents is not routinely helpful in this disease, because myeloma rarely affects organs outside the bones.
To establish the diagnosis of myeloma, the doctor has to prove that there is plasmacytoma on biopsy of a lesion. He has to prove that bone marrow biopsy contains at least 30% of malignant plasma cells and that there is the monoclonal spike of the paraprotein – vide supra.
