Overestimation of hemoglobin in a patient with an IgA-kappa monoclonal gammopathy

Discrepant serum creatinine concentrations caused by paraprotein interference preceding diagnosis of monoclonal gammopathy of undetermined significance

We report a man in his 70s who presented with discrepant serum creatinine concentrations in different hospitals at the same time. Further examinations of these discrepancies revealed turbidity of the serum sample and, thus, a reagent reaction and false hypercreatinine caused by paraprotein interference were suspected. Serum protein electrophoresis revealed a small amount of monoclonal γ globulin (2.9 g/L), which may have been involved in paraprotein interference. Monoclonal λ-type IgG was detected in the serum, resulting in a diagnosis of monoclonal gammopathy of undetermined significance. Previous studies indicated paraprotein interference in serum containing monoclonal IgM or a large amount of IgG (> 25 g/L). Although this case of paraprotein interference induced by a small amount of IgG is rare, a discrepancy in creatinine results may be an indicator leading to the diagnosis of plasma cell proliferative diseases.

Unreliable Automated Complete Blood Count Results: Causes, Recognition, and Resolution

Automated hematology analyzers generate accurate complete blood counts (CBC) results on nearly all specimens. However, every laboratory encounters, at times, some specimens that yield no or inaccurate result(s) for one or more CBC parameters even when the analyzer is functioning properly and the manufacturer’s instructions are followed to the letter. Inaccurate results, which may adversely affect patient care, are clinically unreliable and require the attention of laboratory professionals. Laboratory professionals must recognize unreliable results, determine the possible cause(s), and be acquainted with the ways to obtain reliable results on such specimens. We present a concise overview of the known causes of unreliable automated CBC results, ways to recognize them, and means commonly utilized to obtain reliable results. Some examples of unreliable automated CBC results are also illustrated. Pertinent analyzer-specific information can be found in the manufacturers’ operating manuals.

Evaluation of Double M-Band on Serum Protein Electrophoresis Simulating Biclonal Gammopathy: A Case Report

Multiple myeloma is characterized by the presence of M-protein (monoclonal) in blood or urine. These proteins are immunoglobulins which are produced by a clone of abnormally proliferating B-lymphocytes and/or plasma cells. To evaluate M-protein, serum protein electrophoresis (SPEP) is used where a single band, known as M-band is seen. This band is usually seen in the gamma globulin region. However, in rare entities like biclonal gammopathy, two M-bands appear simultaneously at different positions on SPEP which may be attributed to the clonal expansion of two different neoplastic cell lines. Here, we describe an atypical case of IgA-kappa multiple myeloma, where two M-bands (one in the beta region and one in the gamma globulin region) were found during SPEP. This simulated a picture of biclonal gammopathy. However the monoclonal nature of this M-protein was proved by performing immunofixation electrophoresis (IFE). Further, we put across images to explain how IFE helps in differentiating between apparent and true biclonality.

The interference of monoclonal antibodies with laboratory diagnosis: clinical and diagnostic implications

Diagnostic test interference is due to the presence of material that falsely changes an analytic test result. The development of monoclonal antibodies is discussed with focus on their extensive use as both therapeutic and diagnostic agents. In this review the interference of monoclonal antibodies with laboratory test methods and the potential impact on clinical care is addressed. Recognition of the types of interference, endogenous and exogenous, and the varied mechanisms by which monoclonal antibodies may cause interference are discussed in this report. Review of the literature identifies cases which exemplify the issues facing laboratorians and clinicians and describe the impact on patients. Approaches to reducing and eliminating sources of interference are also addressed. Education of ordering clinicians concerning the possibility of interference in at-risk patients is key in limiting the impact on care. Laboratorians and medical practitioners should be cognizant of the risk of interference to avoid incorrect management of patients.

Artifactual laboratory abnormalities in patients with paraproteinemia

Paraproteinemia, most often as a result of monoclonal gammopathy of unknown significance (MGUS), is very common and its prevalence is expected to increase with the aging of the population. Paraproteins can be associated with a variety of laboratory abnormalities. These may occur as a result of the underlying disease process that causes paraproteinemia, or may result from the paraproteins affecting a physiologic function in vivo. Laboratory abnormalities may also occur artifactually as a result of interference by the paraproteins with a laboratory test in vitro. A wide variety of laboratory tests may be affected, including several commonly obtained tests such as blood counts, serum sodium, calcium, phosphorous, and high-density lipoprotein (HDL) cholesterol. There is poor correlation between the concentration or type of paraproteins and the likelihood of interference. Awareness of this possibility is important so as to avoid erroneous diagnostic conclusions or unnecessary testing.

Spurious counts and spurious results on haematology analysers: a review. Part II: white blood cells, red blood cells, haemoglobin, red cell indices and reticulocytes

Haematology analysers provide quick and accurate results in most situations. However, spurious results, related either to platelets (part I of this report) or to other parameters from the cell blood count (CBC) may be observed in several instances. Spuriously low white blood cell (WBC) counts may be observed because of agglutination in the presence of ethylenediamine tetra-acetic acid (EDTA). Cryoglobulins, lipids, insufficiently lysed red blood cells (RBC), erythroblasts and platelet aggregates are common situations increasing WBC counts. In most of these instances flagging and/or an abnormal WBC differential scattergram will alert the operator. Several situations lead to abnormal haemoglobin measurement or to abnormal RBC count, including lipids, agglutinins, cryoglobulins and elevated WBC counts. Mean (red) cell volume (MCV) may be also subject to spurious determination, because of agglutinins, excess of glucose or salts and technological considerations. In turn, abnormality related to one measured parameter will lead to abnormal calculated RBC indices: mean cell haemoglobin content (MCHC) is certainly the most important RBC indices to consider, as it is as important as flags generated by the haematology analysers (HA) in alerting the user to a spurious result. In many circumstances, several of the measured parameters from CBC may be altered, and the discovery of a spurious change on one parameter frequently means that the validity of other parameters should be considered. Sensitive flags now allow the identification of several spurious counts, but only the most sophisticated HA have optimal flagging and more simple HA, especially those without a WBC differential scattergram, do not possess the same sensitivity for detecting anomalous results. Reticulocytes are integrated now into the CBC in many HA, and several situations may lead to abnormal counts.

Protein precipitation as a possible important pitfall in the clinical chemistry analysis of blood samples containing monoclonal immunoglobulins: 2 case reports and a review of the literature

Two case reports are presented, both illustrating an analytical interference caused by monoclonal immunoglobulins. Falsely low results were obtained in the routine analysis of glucose, CRP and HDL-cholesterol. When analysing samples containing paraproteins, various problems can be encountered in the clinical laboratory: next to the antibody effect, pseudohyponatraemia, hyperviscosity, cryoglobulinaemia and gel formation have to be taken into account. In our two cases the interference was caused by paraprotein precipitation, causing an increased turbidity and an apparent increase of light absorbance at every wavelength due to light scattering, including the wavelengths used in the clinical chemistry assays. We review the literature on this sometimes overlooked interference in photometric/turbidimetric assays. This reaction is based on the insolubility of these proteins in specific physico-chemical circumstances in which many variables are involved, among others: pH and ionic strength, presence of preservatives and surfactants in the assays, pI and other specific properties of the monoclonal immunoglobulins. The complexity of the problem makes predicting or preventing this probably infrequent interference usually impossible. This artifact can cause both false positive and false negative results in multiple parameters (e.g. bilirubin, creatinine, iron, urea, uric acid), the most frequently reported analyte being phosphate. The Sia water test (Sia euglobulin precipitation test) can provide a first clue to a paraprotein aggregation; confirmation can be obtained by observing the time/ absorbance curves of the analysis, performing the test manually or setting up a serial dilution of the sample. The problem can be solved by avoiding the presence of the proteins in the assay, performing the analysis using an alternative method or diluting out the interference. Both laboratorians and clinicians should be aware of interferences in the clinical laboratory since the clinical consequences could be important.

Artifactual hyperbilirubinemia due to paraprotein interference

CONTEXT

Paraprotein interference in automated chemistry is uncommon. We describe 2 patients with paraproteinemia and elevated total bilirubin levels measured erroneously using the Roche total bilirubin assay.

OBJECTIVES

To explain the mechanism of this artifactual hyperbilirubinemia and to determine its frequency in patients with monoclonal or increased immunoglobulins.

MATERIALS AND METHODS

The assay was performed manually using serum from 2 index patients and from control patients (without M proteins). Total bilirubin was also determined using another manufacturer's assay. A prospective study was then undertaken using serum from 100 consecutive patients with various monoclonal gammopathies and from 13 patients with polyclonal hypergammaglobulinemia and cryoglobulins. For all patients, serum immunoglobulin (Ig) G, IgA, IgM, total and direct bilirubin, creatinine, and a direct spectrophotometric assessment of icterus were measured.

RESULTS

After the addition of assay reagents, a white precipitate formed in the reaction mixtures containing serum from the index patients, but not in other samples. This turbidity, rather than the expected color change to pink, increased the absorbance and falsely elevated the total bilirubin value. Serum from both index patients was anicteric, their direct bilirubin measurements were unaffected, and total bilirubin measured using an alternate assay was normal. Among the 113 patients studied, no additional spurious total bilirubin values were detected.

CONCLUSION

Paraprotein interference with the Roche automated total bilirubin assay is caused by precipitate formation. This interference is rare and probably idiosyncratic. Spurious hyperbilirubinemia from paraprotein interference may cause clinical confusion. If artifactual elevation of total bilirubin is suspected, the laboratory should examine the specimen for icterus (manually or by spectrophotometry) or measure total bilirubin using a different method.