AimTo evaluate the clinical utility of incorporating a novel heavy/light chain immunoassay (HLC) into the existing methods for the assessment of multiple myeloma (MM) patients.MethodsConvenience sera samples from 90 previously treated IgG and IgA MM patients in different disease stages were analyzed. The study was conducted in Clinical Hospital Center Zagreb between 2011 and 2013. The collected sera were analyzed by standard laboratory techniques (serum protein electrophoresis, quantification of total immunoglobulins, serum immunofixation, serum free light chain [FLC] assay) and HLC assay.ResultsHLC ratios outside the normal range were found in 58 of 90 patients, including 28 out of 61 patients with total immunoglobulin measurements within the normal range and 5 out of 23 patients in complete response. Both elevated HLC isotype level and abnormal HLC ratio correlated with the parameters of tumor burden, including percentage of plasma cells in the bone marrow (P < 0.001 and P = 0.002, respectively) and an abnormal serum FLC ratio (for both P < 0.001). In addition, abnormal HLC isotype level correlated with serum beta-2-microglobulin level (P = 0.038). In terms of prognosis, abnormal HLC isotype level and abnormal HLC ratio were significantly associated with shorter overall survival (P < 0.001 and P = 0.002, respectively). Interestingly, suppression of the uninvolved (polyclonal) isotype pair, but not other non-myeloma immunoglobulin isotypes, was also associated with a shorter overall survival (P = 0.021). In a multivariate analysis, an abnormal HLC ratio and β2-microglobulin level >3.5mg/L were independent risk factors for survival.ConclusionThe new HLC assay has greater sensitivity in detecting monoclonal protein, correlates with tumor burden markers, and affects patients' outcome.

Introduction: Our aim was to compare analytical specifications of two assays (monoclonal vs. polyclonal) for free light chains (FLCs) quantification optimized for two different analytical platforms, nephelometer ProSpec (Siemens, Erlangen, Germany) and turbidimetric analyser Optilite (The Binding Site, Birmingham, UK). Materials and methods: The evaluation included verification of the precision, repeatability and reproducibility, estimation of accuracy and method comparison study with 37 serum samples of haematological patients. Kappa and lambda FLC were measured in each sample by both methods and kappa/lambda ratio was calculated. Results: Results show satisfactory precision of both methods with coefficients of variation for ProSpec of CVwr = 2.20% and CVbr = 3.44%, and for Optilite CVwr = 2.82% and CVbr = 4.15%. Estimated bias for FLC lambda was higher on the ProSpec analyser, but bias for FLC kappa was higher on the Optilite analyser. Correlation coefficients were 0.98; P < 0.001 for FLC kappa and 0.97; P < 0.001 for FLC lambda. Considering normal/pathological FLC ratio moderate agreement within assays was detected (κ = 0.621). When the results were categorized according to criteria for progressive disease, 4/37 (0.10) cases were differently classified. Lambda FLC values by Optilite in three samples with monoclonal FLC lambda were more than twelve times higher than by ProSpec. A 25% difference in FLC ratio was detected in 16/37 (0.43) and 50% difference in 13/37 (0.35) patients. Conclusions: All manufacturers’ precision claims could not be achieved in the verification study. The comparison of results to biological variations data showed that coefficients of variations are acceptable for both assays. The assays should not be used interchangeably in haematological patients.

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SAŽETAKLaboratorijski nalazi imaju široku primjenu u medicini, od postavljanja dijagnoze bolesti, praćenja tijeka bolesti do praćenja uspješnosti terapije. Za racionalnu interpretaciju laboratorijskih nalaza potrebno je poznavanje referentnih intervala. Referentni interval obuhvaća vrijednost između gornje i donje referentne granice, uključujući i vrijednost samih granica. Najčešće je upotrebljavani i preporučeni oblik referentnog intervala 95-postotni interval koji obuhvaća 95 % središnjih vrijednosti omeđenih 2,5. i 97,5. percentilom. Za izradu referentnih vrijednosti treba odabrati: referentne osobe koje čine referentnu populaciju, referentni uzorak u kojem se određuju referentne vrijednosti koje pokazuju referentnu distribuciju iz koje se zatim izračunavaju donje i gornje referentne granice koje omeđuju referentne intervale. Određivanje referentnih vrijednosti i intervala treba provesti na velikom broju zdravih ispitanika, što predstavlja dugotrajan i skup proces. Zato se u laboratorijskoj praksi upotrebljavaju uglavnom referentne vrijednosti i intervali koje navodi proizvođač korištenih testova. Prema preporukama struke, svaki laboratorij mora verificirati referentne intervale proizvođača kako bi provjerio jesu li su prikladni za namijenjenu populaciju bolesnika. Referentne intervale moguće je provjeriti na nekoliko načina i važno je da se provjera ponavlja periodično odnosno jednom godišnje ili pri promjeni bilo kojih uvjeta koji mogu znatno utjecati na primjenjivani referentni interval. Od nekoliko preporučenih postupaka najčešće se primjenjuje provjera na 20 uzoraka zdravih ispitanika.

Haemoglobinopathies are hereditary disorders of globin chain synthesis and are the most common inherited diseases worldwide. Haemoglobin E is a structural haemoglobin variant characteristic for South East Asian population. We present a rare and unusual finding of haemoglobin E detected in University Hospital Centre Zagreb by capillary zone electrophoresis. Detection of haemoglobin structural variant helped to avoid misdiagnosis of sideropenic anemia and thus potentially harmful therapeutic intervention. In today’s European multiethnic population haemoglobinopathies are a public health issue and Croatian laboratory professionals should be aware of a possibility of finding an unusual haemoglobin pattern.