When an Analytical Interference Is a Useful Diagnostic Tool: Finding Monoclonal Gammopathies in Routine Analysis

Dramatically prolonged coagulation screening tests in a patient with positive lupus anticoagulant and monoclonal immunoglobulin M without bleeding manifestations

BACKGROUND

Concomitant presence of lupus anticoagulant (LA) and monoclonal immunoglobulin in the same patient is uncommon and the influence of this finding on coagulation results is still unknown.

CASE REPORT

We present a patient with a diagnosis of systemic lupus erythematosus (SLE) and secondary antiphospholipid syndrome (APS) with permanently positive LA who presented with accidental finding of newly discovered monoclonal IgM in a high concentration and dramatically prolonged prothrombin time (PT) and activated partial thromboplastin time (aPTT), without bleeding manifestations.

CONCLUSION

Concomitant presence of extremely prolonged PT and aPTT with unusual coagulation reaction kinetics, consistent LA ratio over the follow-up period and normalization of coagulation screening results with decreasing monoclonal IgM concentration elicited suspicion that PT and aPTT prolongation could be attributed to M-protein with antiphospholipid specificity. Low LA-sensitive aPTT reagent Actin FS demonstrated exceptional sensitivity, whereas human placental thromboplastin in contrast to recombinant reagents showed significantly lower sensitivity to monoclonal IgM with antiphospholipid specificity. Changes in the activity of SLE observed during the follow-up period were inversely related to monoclonal IgM concentration, while the presence of secondary APS was consistent. Described analytical interference on PT and aPTT without bleeding manifestation should point towards suspicion of previously unidentified monoclonal IgM with antiphospholipid sensitivity.

Pseudohyponatremia and falsely increased serum osmolal gap caused by paraprotein in a patient with severe metabolic acidosis – a case study

Introduction: The aim of the study is to present a case study of a 63-year-old male with pseudohyponatremia, falsely increased serum osmolal gap and severe metabolic acidosis.

Material and Methods: Venous whole blood (direct sodium selective electrode measurement) and serum (indirect sodium selective electrode measurement) were used to measure sodium concentration. Serum cholesterol, triacylglycerides and total protein were measured to confirm pseudohyponatremia. Base excess in extracellular fluid and serum bicarbonate concentrations were employed as markers of metabolic acidosis. Serum protein electrophoresis and free light chain analysis were used for the detection of paraproteins.

Results: Venous whole blood acid base analysis showed a pH of 7.171, negative base excess in extracellular fluid of – 18.6 mmol/L and sodium concentration of 140 mmol/L. Serum test measurement revealed serum sodium concentration of 130 mmol/L, osmolal gap of 24 mmol/kg, creatinine concentration of 702 µmol/L, HCO3- concentration of 6.1 mmol/L and total protein concentration of 134.9 g/L. Serum paraprotein IgG kappa with a concentration of 86 g/L and a serum free light chains kappa/lambda ratio of 223.5, along with the final diagnosis of multiple myeloma were detected. Toxic alcohol ingestion was considered, both methanol and ethylene glycol tests were negative.

Conclusions: High paraprotein concentrations in serum may lead to pseudohyponatremia when measured by indirect ion selective electrodes. Multiple myeloma frequently leads to renal failure with metabolic acidosis.

Contribution of the laboratory to a diagnosis process by sequential reflective testing: Paraprotein interference on a direct bilirubin assay

Errors in laboratory medicine occur in the preanalytical, analytical, and postanalytical phases. The errors are mostly detected in the preanalytical period. However, analytical errors are still an important source of error, despite their frequency is reduced significantly in years thanks to developments in laboratories. In this case, an analytical error was noticed during the verification of a patient’s results. The direct bilirubin of a 66-year-old male patient admitted to the emergency department was higher than the total bilirubin. The patient’s symptoms were fatigue and dyspnoea. Albumin and haemoglobin (Hb) concentrations of the patient were significantly low. After considering the patient’s demographics and laboratory results, the laboratory specialist suspected a paraproteinemia interference. Total protein was performed as a reflective test. The albumin/globulin ratio was reversed. Thereafter, serum protein electrophoresis (SPEP) and immunofixation electrophoresis (IFE) were performed as another reflective tests, respectively. SPEP and IFE results were in favour of monoclonal gammopathy. The patient was directed to a haematologist, underwent a bone marrow biopsy, and the result was reported as Waldenstrom’s macroglobulinemia with plasma cell differentiation expressing IgM-Kappa. The patient went on a chemotherapy protocol, and his condition has been improved in subsequent months. Detection of analytical errors is of great importance, like in our case, and may be used as a tool to identify patients who have not yet been diagnosed. The laboratory specialist must dominate the entire process of each test in the laboratory, be aware of the limitations of tests, and turn these disadvantages into advantages when necessary.

Understanding and managing interferences in clinical laboratory assays: the role of laboratory professionals

The recently raised concerns regarding biotin interference in immunoassays have increased the awareness of laboratory professionals and clinicians of the evidence that the analytical phase is still vulnerable to errors, particularly as analytical interferences may lead to erroneous results and risks for patient safety. The issue of interference in laboratory testing, which is not new, continues to be a challenge deserving the concern and interest of laboratory professionals and clinicians. Analytical interferences should be subdivided into two types on the basis of the possibility of their detection before the analytical process. The first (type 1) is represented by lipemia, hemolysis and icterus, and the second (type 2), by unusual constituents that are not undetectable before analysis, and may affect the matrix of serum/plasma of individual subjects. Type 2 cannot be identified with current techniques when performing the pre-analytical phase. Therefore, in addition to a more careful evaluation and validation of the method to be used in clinical practice, the awareness of laboratory professionals should be raised as to the importance of evaluating the quality of biological samples before analysis and to adopt algorithms and approaches in the attempt to reduce problems related to erroneous results due to specific or non-specific interferences.