Case Study. Accidental Diagnosis of Multiple Myeloma in a 44-Year-Old White Woman due to Erroneous Results via Chemical Analyzers.

Transcription

1 Accidental Diagnosis of Multiple Myeloma in a 44-Year-Old White Woman due to Erroneous Results via Chemical Analyzers Ola Bashiti, MLS(ASCP) CM Laboratory Medicine 47:1:5-11 CLINICAL HISTORY Patient: 44-year-old white woman. Chief Complaints: Cramping, nausea, shortness of breath, visual disturbances ( seeing yellow dots ). Medical History: Status asthmticus, tobacco use, hypertension, migraines. Case Description The patient, a 44-year-old white woman, arrived at the emergency department of St. Vincent s Medical Center with an array of symptoms, including cramping and visual disturbances (she reported seeing yellow dots ). Her medical history included hypertension and migraines. Because maintenance was being performed on the main analyzer in our laboratory, the AU680 (Beckman Coulter), the chemistry laboratory assayed the serum specimen from the patient on the Abbott i-stat (Abbott Laboratories Inc.). When the test results showed the analyte levels of the patient to be within normal limits, she was released and Abbreviations Ig, immunoglobulin; ISE, ion-selective electrode; MM, multiple myeloma; CBC, complete blood count; RBC, red blood cell; MCV, mean corpuscular volume; MCHC, mean corpuscular hemoglobin concentration; FLCs, free lights chains; WBC, white blood cell; HGB, hemoglobin; HCT, hematocrit; MCH, mean cell hemoglobin; RDW, red-blood-cell distribution width; PLT, platelet; MPV, mean platelet volume; SP, serum protein; G., Immunoglobulin G; A, Immunoglobulin A; M, Immunoglobulin M. St. Vincent s Medical Center, University of North Florida, Jacksonville, FL Principle Laboratory Findings: Tables 1 7, Figures 1 4. Keywords: pseudohyponatremia, ion-selective electrode, electrolyte exclusion effect, direct potentiometry, indirect potentiometry, monoclonal gammopathy, multiple myeloma returned home. After the maintenance had been completed, I ordered the same specimen to be assayed on the AU680. Due to the low sodium levels and conflicting results recorded by the 2 analyzers, the physician called the patient back to the emergency department. Another specimen was ordered and tested on the AU680 and the i-stat. The results on the AU680 showed once again to be critically low, and those yielded by the i-stat were normal. The serum specimen was retested to determined protein and albumin values. I observed that the protein level in the specimen was high and the albumin level was low. I questioned these results and was advised by the clinical chemist that the patient might be harboring a plasma cell neoplasm. A serum protein electrophoresis was ordered for the patient, to confirm or contradict her condition. Immunofixation electrophoresis and immunoglobulin quantification was carried out due to the outcome of serum protein electrophoresis. Bone marrow studies confirmed 95% cellular bone marrow that appeared to be composed of approximately 30% plasma cells. Follow-up hematology studies were completed to assist with bone marrow studies. Questions *To whom correspondence should be addressed. olabashiti@yahoo.com 1. Based on the data in the chemical analysis tables, what is/ are the patient s most significant results? VC American Society for Clinical Pathology All rights reserved. For permissions, please journals.permissions@oup.com e5

2 2. Given the patient s medical history, how can her test results be explained? What is the reason for the difference in sodium levels using each method of analysis? 3. Why is the discrepancy between the sodium results important? 4. What do the additional test results indicate? What disorders are associated with the findings? 5. What is the patient s final diagnosis? 6. What is the clinical significance of the suppressed immunoglobulin (Ig)M and IgA in this patient? 7. Why is the patient s case clinically significant? Answers 1. There is a wide difference in the sodium values reported by each instrument. The istat/gem shows a normal sodium value, and the AU680 presents a decreased sodium value. The potassium level is slightly low, according to both instruments, and the anion gap and total calcium are very low. Further tests reveal a profoundly high protein level and low albumin level. 2. The sodium value reported using the AU680 is described as hyponatremia, or low sodium levels in the blood. It has been reported that hyponatremia can be observed in plasma with extremely high protein values 1 ; however, it is usually classified as pseudohyponatremia. Pseudohyponatremia is defined as spuriously low plasma sodium concentration. 2 The measured sodium concentration is low, but the actual sodium concentration in the plasma is normal. This measurement artifact is evident in cases of extremely high levels of lipids (hyperlipidemia) or proteins (hyperproteinemia) in the blood. However, hyperlipidemia is a much more common cause for pseudohyponatremia because it represents an increase in triglyceride and cholesterol levels, which is found in prevalent medical conditions like diabetes mellitus, kidney disease, and hypothyroidism. Table 1. Chemical Analysis Using Direct Potentiometry Analyte Patient Result Normal Values Sodium 122 mmol/l mmol/l Potassium 3.4 mmol/l mmol/l Chloride 98 mmol/l mmol/l Bicarbonate 25 mmol/l mmol/l Anion gap 2 mmol/l 9-22 mmol/l Glucose 4.66 mmol/l mmol/l Blood urea nitrogen 3.93 mmol/l mmol/l Creatinine 80 mmol/l mmol/l Ca 1.98 mmol/l mmol/l Albumin-corrected Ca 2.50 mmol/l mmol/l Table 2. Chemical Analysis Using Indirect Potentiometry Procedure Patient Result, mmol/l Normal Values, mmol/l Sodium Potassium Chloride Bicarbonate Anion gap Glucose Blood urea nitrogen Creatinine Ca Albumin-corrected Ca Table 3. Protein and Albumin Results. Procedure Patient Result, g/dl Normal Values, g/dl Protein Albumin < Table 4. Protein Quantification for Patient Serum Electrophoresis Fraction Patient Result, % Normal Values, % Albumin Alpha Alpha Beta Gamma Approximately 93% of plasma is composed of water and 7% of solids. 3 Free electrolytes are part of the water portion, and proteins and lipids make up the solid portion. In cases of hyperproteinemia or hyperlipidemia, the solid component takes up most of the total plasma, causing the water component to be greatly reduced. Pseudohyponatremia is caused by the electrolyte exclusion effect that is found using indirect methodology because the sodium electrolytes become limited to a smaller volume of water. 4 e6 Lab Medicine 2016;47:1;

3 Table 5. Complete Blood Count for Patient s Blood Cell Patient Result Normal Values WBC /L /L RBC /L /L HGB 7.9 g/dl g/dl HCT 24.4% 36.0%-46.0% MCV 84.4 fl fl MCH 27.2 pg pg MCHC 32.2 g/dl g/dl RDW 24.1% 11.5%-14.5% PLT /L /L MPV 8.7 fl fl WBC, white blood cell; RBC, red blood cell; HGB, hemoglobin; HCT, hematocrit; MCV, mean corpuscular volume; MCH, mean cell hemoglobin; MCHC, mean cell hemoglobin concentration; RDW, red blood cell distribution width; PLT, platelet; MPV, mean platelet volume. Table 6. Immunoglobulin Quantification Results Immunoglobulin Type Patient Result, mg/dl Normal Values, mg/dl M < A < G 10, My patient presents with a very high level of protein that was nonexistent in her medical history, which implicates pseudohyponatremia. Potassium and chloride are influenced by the electrolyte exclusion effect in the same manner as sodium because they are electrolytes contained in the water portion of plasma and are measured using the same methodology. The patient s potassium and chloride levels were borderline low, which was most likely caused by the hyperproteinemia. The anion gap evaluates the difference between measured and unmeasured anions in the plasma and is usually used to assess acid-base disorders or to provide quality control for measuring all electrolytes. The calculation for anion gap is Na - [Cl þ Bicarbonate]. The patient s anion gap is significantly decreased. Low values are an infrequent finding and most commonly indicate laboratory error or hypoalbuminemia (low albumin in the blood). Laboratory errors occur when there is an underestimated sodium concentration due to elevated proteins in the plasma. Hypoalbuminemia is the second most common cause of a low anion gap. The negative charges of albumin make up most of the unmeasured anions, so changes in the plasma albumin would be expected to alter the plasma anion gap. Studies have found that for every 1 g/dl decrease in albumin, there is a 2.3- to 2.5-mmol/L decrease in the anion gap. 4 In this case, both causes can be applicable to the patient s status because the patient demonstrated pseudohyponatremia and hypoalbuminemia. Albumin has a direct effect on calcium. Half of the calcium in the blood is free and metabolically active. The remaining half is bound to albumin, with a smaller amount complexed to anions, and is metabolically inactive. The total calcium measurement represents the free and bound forms, whereas the ionized calcium measurement represents the metabolically active form. Because half the calcium in the blood is bound to albumin, total calcium test results are influenced by any fluctuation in albumin levels. In fact, each 1 g/dl decrease in plasma albumin level will lower the total calcium level by approximately 0.25 mmol/l. Ionized calcium will not be affected, making it a more ideal test for measuring calcium levels. 5 The hypoalbuminemia experienced by the patient explains the low calcium (hypocalcemia) result obtained using the AU680. The i-stat provided a normal ionized calcium level, indicating that the patient does not have any calcium disorder and is showing pseudohypocalcemia. The disparity in sodium values between the 2 analyzers is due to a difference in the methodology of potentiometry. Potentiometry is the measurement of potential difference between 2 electrodes. The ion-selective electrode (ISE) is a potentiometric electrode that is most commonly used in laboratories to estimate the concentration of specific electrolytes in blood specimens. ISEs use high-impedance voltmeters to measure the electrical potential generated between a measuring electrode and a reference electrode when the activity of a specific ion is dissolved in a solution. 4 There are 2 types of ISEs: direct and indirect. The direct method analyzes whole blood and does not involve a predilution, and the indirect method involves automatic dilution of the plasma specimen. 1 The istat uses the direct method and the AU680 uses the indirect method. Essentially, electrolyte concentrations are represented by the total plasma level, which includes dissolved solids and water. However, the clinically significant sodium value is the plasma water concentration. 6 The values in total plasma usually correlate with that in plasma water, except in cases of high levels of proteins or lipids in the plasma specimen Lab Medicine 2016;47:1;5 11 e7

4 Figure 1 Serum protein electrophoresis pattern for normal control, abnormal control, and specimen from the patient, a 44-year-old white woman. Albumin Alpha 1 Alpha 2 Figure 2 Normal densitometric tracing. Beta Gamma when using indirect methods; the values will be falsely decreased. The indirect method of ion-selective electrode potentiometry is affected by the electrolyte exclusion effect because it assumes that all plasma specimens contain 93% water and that the volume of specimen material added to the diluent is corrected for dilution based on this volume. The measured concentration is modified by a factor of 0.93 to achieve the true sodium ion concentration in plasma. In a specimen with hyperproteinemia, the extra proteins take up volume and displace water so that plasma contains less water per unit volume and fewer electrolytes per unit volume. Excess dilution occurs because the same amount of diluent is added but to a lower water component. Therefore, less sodium is drawn from the plasma, resulting in an underestimated electrolyte concentration. 7,8 The decrease in the amount of water per volume of plasma due to hyperproteinemia can be explained using the following equation: Serum Water ð%þ ¼ 99:1 ð0:73 protein concentration in g=dlþ ¼ 99:1 ð0:73 15:8Þ ¼ 99:1 11:53 ¼ 87:6 ðor e88%þ The decrease in plasma water content is 100% % ¼ 12.4%. Therefore, a 12.4% volume displacement affects the actual sodium concentration. 2 The direct ion-selective electrode compensates for false hyponatremias that are encountered in the indirect method because it is not susceptible to the electrolyte exclusion effect. Direct potentiometry does not involve a dilution step so it measures the activity of sodium in the water phase rather than the total sodium concentration. The final electrolyte value is independent of the protein (solid) content in the plasma Hyponatremia is the most common disturbance in blood chemistry. Usually, it is mild, self-limiting, and not associated with symptoms. However, severe hyponatremia can occur in serious conditions associated with neurological symptoms. 9 The symptoms reported by the patient were possible indications for true hyponatremia. The decreased sodium value produced by the reference analyzer could have led to misdiagnosis and, consequently, improper treatment. The patient was initially called back to the emergency department to be treated for hyponatremia, which was, in fact, pseudohyponatremia, which should not be treated. Managing false hyponatremia can lead to clinical errors, with potentially serious consequences, including death. 4. The serum protein electrophoresis pattern demonstrates a defined gamma band for the patient s serum that resembles the abnormal control, which is known as a monoclonal protein spike. Protein quantification shows a decreased albumin fraction, hypoalbuminemia, and an increased gamma fraction (hypergammaglobulinemia). These results are also illustrated in the densometric tracings. The most e8 Lab Medicine 2016;47:1;

5 Albumin Alpha 1 Alpha 2 Beta Gamma Figure 3 Densitometric tracing in the patient, a 44-year-old white woman. Figure 4 Immunofixation electrophoresis results in the patient, a 44-year-old white woman. SP indicates serum protein; G, Immunoglobulin G; A, Immunoglobulin A; M, Immunogobulin M. prominent finding is the homogenous spike-like peak in the gammaglobulin zone, which is expressed in manifestations of monoclonal gammopathies. Monoclonal gammopathies are part of a group of plasma cell disorders in which an immunoglobulin from a single plasma cell clone is produced in excess, generating a homogenous M protein spike. An M spike is characterized by the presence of a well-defined band with a single heavy chain and a band with a light chain. Monoclonal gammopathic diseases can range from a relatively benign condition to malignant conditions such as multiple myeloma (MM). Therefore, MM must be differentiated from other monoclonal gammopathic conditions, such as lymphoplasmacytic lymphoma, plasmacell leukemia, and monoclonal gammopathy of undetermined significance, to evaluate the severity of disease. 10 MM occurs when malignant plasma cells form in the bone marrow, producing an abnormal amount of dysfunctional immunoglobulin. 11 Normal plasma cells help the immune system by producing immunoglobulins that are composed of proteins. Antibodies consist of 2 heavy chains and 2 light chains. There are 5 types of heavy chains, known as immunoglobulin (Ig)G, IgA, IgM, IgD, and IgE, as well as 2 types of light chains, termed kappa and lambda. All the abnormal cells in MM are made up of the same antibody. So, MM can be categorized by the type of light and heavy chains produced. The most common type of heavy chain produced in MM is IgG, followed by IgA and IgD. IgM myelomas are rare, but when IgM is increased in the blood, it is usually associated with Waldenström macroglobulinemia. MM can be differentiated from other monoclonal gammopathies based on features distinctive to each disease, as can be seen in Table Normocytic, normochromic anemia and pancytopenia are common findings in patients with MM because the plasma cells in the bone marrow proliferate extensively and produce tumors that interfere with hematopoiesis The final diagnosis for the patient is multiple myeloma (MM). Distinct features required for the diagnosis of MM include an M-protein spike with a level greater than 3 g/dl, greater than 10% to 15% plasma-cell involvement in the bone marrow, and anemia with pancytopenia. 10 Immunofixation was used to identify the specific type of malignant heavy chain and light chain present (M protein), namely, an immunoglobulin (Ig)G heavy chain and lambda light chain. Immunoglobulin quantification provides a preliminary diagnosis for multiple myeloma (MM) because IgG values were greater than 3 g/dl. The results of bonemarrow studies exhibit 30% plasma-cell involvement, which is a definite diagnosis for MM. The complete blood count (CBC) points out a low red blood cell (RBC) count and a normal mean corpuscular volume (MCV) and mean corpuscular hemoglobin concentration (MCHC), which is considered a normocytic, normochromic type of anemia in which the platelets are decreased, indicating thrombocytopenia. Urine protein studies could have further aided in the diagnosis of MM, but they were not performed. The expected findings would be proteinuria (>1 g of protein) and the presence of Bence-Jones proteins (lambda light chains) in a 24-hour urine collection. 13 Bence-Jones proteinuria is confirmed by urine immunofixation electrophoresis. Bence- Jones proteins are monoclonal kappa or lambda Lab Medicine 2016;47:1;5 11 e9

6 Table 7. Types of Monocolonal Gammopathy, Including Multiple Myeloma Disease Monoclonal gammopathy of undermined significance <10% plasma cell involvement on bone-marrow biopsy No anemia Lymphoplasmacytic lymphoma Hyperviscosity and hypercellular bone marrow Plasma cell leukemia M protein levels are low Multiple myeloma M protein level >3000 mg/dl 10%-15% plasma cell involvement on bone-marrow biopsy Anemia, pancytopenia immunoglobulin free lights chains (FLCs) that are not attached to the heavy-chain portion of the immunoglobulin molecule. Approximately 46% of cases of MM in which the patient produces intact immunoglobulin monoclonal proteins have excess monoclonal FLCs in the urine by immunofixation The suppression of immunoglobulin (Ig)M and IgA is clinically significant because the patient is more prone to acquiring infections. IgM, which encompasses approximately 10% of the Ig pool, is the first antibody produced in an immune response and is responsible for agglutination and cytolytic reactions. IgA accounts for 15% to 20% of the Ig pool and is the primarily found in secretions such as tears, saliva, milk, and intestinal fluids. IgA also plays a primary role in defense against foreign substances. For an infectious disease to develop in the host, the organism must bypass, overcome, or inhibit normal bodily defense mechanisms. A decrease in IgM and IgA puts the patient at a higher risk of recurrent infections because the immune response has a shortcoming in its first lines of defense that recognize and fight off infectious agents. Increased susceptibility in patients with multiple myeloma (MM) mainly results from defective antibody synthesis (M protein) in the bone marrow that crowds out normal plasma cell precursors. In such patients, there is an excess of one particular immunoglobulin that does not fight off infection and a decrease in the normally functional white blood cells; infections are dominantly derived from pneumococci or gram negative bacteria. Pneumonia, pyelonephritis, meningitis, and arthritis are the leading causes for sepsis, which can ultimately lead to death if bacteremia ensues The patient entered the hospital with no relevant history of a serious medical condition. The findings of routine Distinctive Features M protein level <3000 mg/dl Immunogloblin M protein is present Peripheral blood contains >20% plasma cells M protein appears as a narrow spike in gamma, beta, or alpha 2 regions chemistry tests using 2 different methods showed a discrepancy between sodium values, with the result from one assay instrument indicating pseudohyponatremia. The patient should not be treated for false hyponatremia because mistreatment could lead to potentially dangerous consequences. Hence, direct potentiometry should be used to test plasma that has an elevated protein. The laboratory s actions to solve the discrepancy in sodium values ultimately led to the discovery of the patient s underlying multiple myeloma (MM). MM represents 10% of all hematological malignant neoplasms. The patient s demographics (she is a 44-year-old white woman) are unconventional for the diagnosis of MM. The typical age at diagnosis is 66 years, with a higher incidence in African Americans and males. It is difficult to diagnose MM at a time when disease progression can still be controlled because MM usually causes no symptoms until it reaches an advanced stage. Advancing manifestations of the disease induce numerous complications in the body, including anemia, pancytopenia, bone destruction, hypercalcemia, renal failure, and neuropathic occurrences. 12 The patient had already begun displaying signs of early disease advancement with anemia and thrombocytopenia. Therefore, diagnosing MM at the present stage will help stop her disease progression and aid her prognosis. References 1. Levy GB. Determination of sodium with ion-selective electrodes. Clin Chem. 1981;27(8): Higgins C. Pseudohyponatremia. Acutecare testing Web site. etesting.org/en/articles/pseudohyponatremia. Accessed October 16, e10 Lab Medicine 2016;47:1;

7 3. Dhatt G, Talor Z, Kazory A. Letters to the editor: direct ion-selective electrode method is useful in diagnosis of pseudohyponatremia. J Emerg Med. 2012;43(2): Kraut JA, Madias NE. Serum anion gap: its uses and limitations in clinical medicine. Clin J Am Soc Nephrol. 2007;2: Calcium. American Association for Clinical Chemistry Web site. testsonline.org/understanding/analytes/calcium/tab/glance/. Accessed October 16, Spitalnik SL, Arinsburg SA, Jhang JS. Clinical Pathology Board Review. Philadelphia, PA: Elsevier Saunders; p Garibaldi BT, Cameron SJ, Choi M. Pseudohyponatremia in a patient with HIV and hepatitis C coinfection. J Gen Intern Med. 2008;23(2): Ladenson JH, Apple FS, Aguanno JJ, Koch DD. Sodium measurements in multiple myeloma: two techniques compared. Clin Chem. 1982;28(12): Fortgens P, Pillay TS. Pseudohyponatremia revisted: a modern-day pitfall. Arch Pathol Lab Med. 2011;135: O Connell TX, Horita TJ, Kasravi B. Understanding and interpreting serum protein electrophoresis. Am Fam Physician. 2005;71(1): Barrick MC, Mitchell SA. Multiple myeloma: recent advances for this common plasma cell disorder. Am J Nurs. 2001;101(4): About Multiple Myeloma. University of California San Francisco Web site. Accessed October 16, Shah D, Multiple Myeloma Workup. Medscape Web site. cine.medscape.com/article/ workup. Accessed October 16, Turgeon ML. Immunology & Serology in Laboratory Medicine. 5th ed. St.Louis, MI: Elsevier Inc; p Lab Medicine 2016;47:1;5 11 e11