Urine immunofixation electrophoresis and serum free light chain analyses benefit diagnosis of multiple myeloma in orthopedic patients with normal serum total proteins, creatinine, calcium, and hemoglobin.

BACKGROUND: A substantial number of patients with multiple myeloma (MM) who have bone destruction are initially admitted into the orthopedic service at the hospital. However, routine laboratory testing usually fails to identify these patients, thus delaying optimal therapy. Therefore, there is a clear medical need for early diagnosis of MM in these patients. METHODS: Between 2019 and 2021, 42 patients receiving treatment for orthopedic conditions had normal hemoglobin (Hb), total protein (TP), albumin (ALB), creatinine (CREA), and blood calcium (Ca) levels before their surgical procedure(s) but were subsequently pathologically confirmed to have MM, based on their presenting orthopedic symptoms. During the same period, 52 patients with orthopedic conditions were pathologically excluded from the diagnosis of MM and were recruited into our control group. Serum free light chain (sFLC) testing was performed in 94 consecutive patients in the orthopedic service using Siemens N Latex FLC kits. The levels of Hb, TP, ALB, CREA, and Ca were also measured. All 42 patients with MM were divided into group A (n = 25: κ proliferation) and group B (n = 17: λ proliferation) by the pathology department. RESULTS: There were no significant differences in levels of Hb, TP, ALB, CREA, and Ca between group A and group B and the control group. However, the sFLC κ/λ ratio of group A and B was also significantly different from that of the control group (P < .001). The results of serum immunofixation electrophoresis (IFE) testing demonstrated negative results in 14 cases (58.3%) in group A and 4 cases (25.0%) in group B. CONCLUSIONS: Some patients with orthopedic conditions who do not have typical MM laboratory results, such as those with abnormal Hb, TP, ALB, CREA, and Ca levels before their operation(s), actually have MM. MM should be highly suspected in patients with unexplained bone lesions and with an abnormal sFLC κ/λ ratio. Further tissue or bone marrow biopsy is needed in these patients even if serum and urine IFE results are negative and light chain ratio is normal.

Multisite distribution of fibrillary inclusions in a patient with light chain proximal tubulopathy: A case report.

RATIONALE: Light chain proximal tubulopathy (LCPT) is a rare form of renal impairment associated with multiple myeloma (MM). LCPT is caused by inclusions formed of free light chains that are typically crystalline, but can also be noncrystalline structures. PATIENT CONCERNS: A 62-year-old man was hospitalized for the investigation of abnormal urine test results lasting for 1 year and kidney-function abnormalities persisting for more than 1 month. DIAGNOSES: Noncrystalline LCPT and MM. INTERVENTIONS: The patient was treated with the lenalidomide, bortezomib, and dexamethasone and pomalidomide, bortezomib, and dexamethasone chemotherapy regimens. OUTCOMES: Complete remission of MM was achieved, and the patient's renal function returned to normal. LESSONS: This case report highlights the importance of renal pathology in the diagnosis of patients with unexplained chronic kidney disease and proteinuria.

Determinación inmunonefelométrica de cadenas ligeras libres de inmunoglobulinas en orina / Measurement of free light chains inmunoglobulin in urine by a nephelometric inmunoassay

El método se basa en la reacción de inmunoprccipritacion en [ase líquida, con antisueros específicos absorbidos anti-kaprpa y anti—lambda fibre, de NSC (New Scientific Campany).La.s inmnunocomplejos se cuantificaron con un nefelémetro BNA (Beliring Diagnostic), realizándose condiction antisue ros estudios de precisión, linealidad y comparación con otro método. Se obtuvieron CV intraseriales menores del 5%, exceptuando lambda libre a concentración baja (2,8%). Los análisis resultaron lineales hasta una concentración de 300 mg/dl de Kappa libre y de 150 mg/dl. de lambda libre. Se compararon los resultados de Kappa y lamdba libre (NSC) con los de kappa y lambda total (antisueros de Behiring Diagnostic), observándose que los valores obtenidos con orinas normales eran menores que los cut off asignados (≤4,5 K total, ≤2,6 L total, ≤1K libre, ≤0,7 L libre). Las orinas con cadenas ligeras libres policlonales presentaron uno o más resultados mayores que los cut off y las orinas con proteínas Bence Jones mostraron todos los valores más latos de los cut off (AU)

The procedure is based on inmunoprecipitin reactions in a fluid phase of free light chains with adsorbed aintisera, specific for free kappa and lambda chains, of New Scientific Company (NSC). The resulting inmunocomplexes were quantified with a BNA nephelometer (Behring Diagnostic), we have performed studies of reproducibility, linarity and method comparison. Within-run coefficients of variation (CV) were <5% except for free kappa chains at high concentration (CV =12,7%); between-run CV was 2,8% for free lambda chains at low concentration and >5% for the rst the samples. The assays were linear up to concentrations of 300 mg/dl and 150 mg/dl and 150 mg/dl for free Kappa and Lambda chains, respectively. The results for total kappa and lambda chains (Behring) were compared with those for free kappa and lambda (NSC). We have found that normal urines gave concentrations below the cup off values with both antisera (<4,5 mg7del for free kappa, <0,7 mg/dl for free lambda); urines with polychonal light chains showed one or more pathological results, and above the cut off values in all the cases for urines with Bence-Jones proteins (kappa or lambda) (AU)