Free light chains and heavy/light chains in monitoring POEMS patients.

BACKGROUND: POEMS syndrome is defined by Polyneuropathy, Organomegaly, Endocrinopathy, Monoclonal gammopathy and Skin changes. The vascular endothelial growth factor (VEGF) appears to play a key role in the pathogenesis of the syndrome, and its concentrations are deemed to correlate to disease activity. The aim of the present study was to verify whether other biochemical markers including serum free light chains (FLC) and heavy/light chains (HLC) would be of value in monitoring POEMS patients. METHODS: Fifty-three serum samples were collected from seven POEMS patients at diagnosis and during a follow-up period (range 14-56 months). VEGF was measured using an ELISA method, while FLC and HLC concentrations were measured using Binding Site reagents on a BNII (Siemens) nephelometer. RESULTS: At diagnosis all patients presented high VEGF concentrations, while the κ/λFLC ratio (FLCr) was within the reference range. Four patients had abnormal HLC, HLCκ/HLCλ (HLCr) and FLC values. The relationship between the trend of VEGF and both HLC and FLC during the follow-up was analysed by means of Cohen's κ coefficient. VEGF and HLC values displayed a significant κ-Cohen (0.537, p=0.002) in all chemotherapy-responder patients while in non-responders it did not. Conversely, in both responders and non-responders, VEGF and FLC values did not attain a significance on κ-Cohen analysis. In three out of four responders HLCr values increased, thus reflecting an improved clinical condition. CONCLUSIONS: The findings made in the present study indicate that HLC, either as intact immunoglobulin or as HLCr, may provide useful information, particularly in identifying responders and confirm that the role of FLC is unreliable in monitoring patients with POEMS syndrome.

Identification and quantification of hemoglobins in whole blood: the analytical and organizational aspects of Capillarys 2 Flex Piercing compared with agarose electrophoresis and HPLC methods.

BACKGROUND: The present study was conducted to evaluate the analytical performance and the organizational aspects of Capillarys 2 Flex Piercing system (CFP) respect to agarose electrophoresis and HPLC methods in hemoglobinopathies screening. METHODS: The measurement of imprecision in HbA 2 and HbF quantification was verified on HbA 2 CFP control and on three samples; 74 whole blood samples were used to evaluate migration time imprecision of hemoglobin variants S, C and E (HbS, HbC, and HbE); to compare methods, 451 samples were tested on CFP and HPLC; reference values were verified as value distribution in 160 blood donors and at ROC curve analysis on 449 samples from routine analysis. RESULTS: Imprecision: the analytical CV % s ranged from 1.25 to 3.9 at HbA 2 quantification, the CV % was 3.78 at HbF quantification; the running time imprecision for HbS and HbC and HbE ranged from 0.20 to 0.69 % . Method comparison: at regression analysis findings were HbA 2: CFP=1.21×HPLC­0.64, HbF: CFP=1.31×HPLC−0.75, HbS: CFP=1.10×HPLC−3.24. Reference values: the HbA 2 95th percentile range was 2.5­2.8; HbF was undetectable in 154 out 160 samples tested; at ROC curve analysis the best combination of sensitivity and diagnostic efficiency was obtained using 2.2 and 3.0, as reference values, for HbA 2 and 1.1 as the upper reference limit for HbF. Organizational aspects: with respect to the procedures currently implemented in our laboratory CFP requires 2 h less time and obviates the need for some manual steps. CONCLUSIONS: The quantification, reproducibility and diagnostic efficiency provided by CFP in identification and quantification of hemoglobins appear accurate. In addition, the use of primary tubes allows improved safety, and the avoidance of some manual steps, that prolong working time and are a source of possible errors.

Evaluation of a new capillary zone electrophoresis system for the identification and typing of Bence Jones Protein.

OBJECTIVES: Capillary electrophoresis has recently emerged as a new sensitive technique for the separation of urinary proteins. We evaluated a new method for Bence Jones Protein (BJP) detection and characterization on native urine samples by the Paragon CZE 2000 system. To avoid interference in electrophoretic separation, urine samples were preliminarily treated for the selective removal of interfering salt particles. DESIGN AND METHODS: The evaluation was done on a total of 350 fresh 24-h urine samples. The salt particle removal consisted of a manual chromatographic separation, optimized in the course of our evaluation. Capillary zone urinary protein electrophoresis (CZ-UPE) was compared with conventional high-resolution electrophoresis on an agarose gel, while capillary immunosubtraction (CZU-IFE) was compared with agarose gel immunofixation. RESULTS: After finding a consistent protein loss in eluates, the preanalytical treatment was optimized by changing sample dilution and eluate collection. The within- and between-run imprecision values for monoclonal peaks corresponding to BJP ranged from 0.4-12.2% to 3.3-6.3%, respectively. The detection limit for BJP, defined as the lowest measurable monoclonal peak on CZ-UPE, was 0.0012 g/L for kappa BJP and 0.0007 g/L for lambda BJP. CZ-UPE and CZU-IFE sensitivities were significantly lower in urine samples with a total protein level < or = 100 mg/L (67% and 78%, respectively) compared to those with total protein >100 mg/L (92% and 94%, respectively). Comparison between BJP measurements obtained from densitometric scanning with those from absorbance tracing showed a correlation coefficient of 0.994 and a bias of 29.8 mg/L. CONCLUSIONS: Paragon CZE 2000 can be introduced in routine for screening and typing of BJP; in urine samples with a total protein level >100 mg/L, the performance is consistent with results from published validation studies on CZE applied to serum samples.

Anti-heparan sulphate antibodies and homocysteine in dementia: markers of vascular pathology?

Increasing evidence supports a pathogenic role of heparan sulphate (HS) in the development of dementia. Since HS proteoglycans are present in the endothelial cells and perivascular basement membrane, we wanted to assess blood titres of HS antibodies (Abs) in patients with vascular dementia (VD) and in patients with Alzheimer's disease (AD) with cerebrovascular disease (CVD) [mixed dementia (MixD)]. Moreover, plasma levels of homocysteine, an independent risk factor for the development of dementia as well as for CVD, were also determined. High HS Abs titres were present in one patient with VD and in two patients with mixed dementia, as well as in two neurological control patients (stroke and epilepsy). Increased homocysteine levels were found in 62.5% of patients with mixed dementia, in 22.2% of the VD subjects, in 54.2% of patients with CVD, and in 41.2% of patients with other neurological diseases. The present findings suggest that neither elevated HS Abs titres nor increased homocysteinemia may represent a useful biochemical marker for the diagnosis of VD.

An IgE multiple myeloma: contradictory findings in clinical laboratory testing.

BACKGROUND: IgE multiple myeloma is a rare kind of plasma cell disorder, characterized by an aggressive clinical course, where laboratory testing plays a fundamental role for the correct diagnosis in order to start a targeted therapy. In the present paper it is described a case of IgE myeloma where contradictory findings between immunometric and separative techniques were found. MATERIALS AND METHODS: Serum and 24h urine samples were tested using electrophoresis and immunofixation electrophoresis employing IgE antiserum and IgE were quantified using an immunometric method. RESULTS: Serum immunofixation evidenced a monoclonal band ascribable to IgE lambda and IgE serum concentration was 1,364,00 kU/L. Urine electrophoresis evidenced a band compatible with IgE, and urine concentration was 2715 kU/L. On the contrary in the immunofixation of the urine sample no band reacting with IgE antiserum was found. CONCLUSIONS: Considering that the immunometric method measured IgE in urine sample and the electrophoresis of urine sample evidenced a band compatible with IgE, the explanation could be that during renal filtration or because of some characteristics related to urine matrix, the immunoglobulin IgE could had been modified in the site recognized by the antiserum used in immunofixation, and not in the one used in the immunometric method.

Serum free light chain reference values: a critical approach.

OBJECTIVES: The clinical usefulness of serum free light chain (FLC) measurement in the management of patients with plasma cell proliferative disorders has been reported in several papers, and most clinical studies use the reference ranges declared by the manufacturer. The aim of the present study was to evaluate the reproducibility of FLCs immunoassay and to validate the reference range, before introducing it in routine setting. DESIGN AND METHODS: Internal quality control materials and a pool of fresh serum samples were used to evaluate imprecision; 162 fresh sera from healthy blood donors were analyzed to evaluate the reference range for FLCs. In order to verify the κ/λ FLC ratio, 43 sera from patients with polyclonal hypergammaglobulinemia were tested. The FLC immunoassay was performed using a nephelometer with the Freelite reagents. RESULTS: The imprecision studies performed using a serum pool tested with two different lots of reagents showed a mean CV of 16.09% for κFLC and of 16.72% for λFLC. Lower CV%s and different mean values were found by calculating the results from each specific lot separately, while different results were obtained using the control materials provided by the manufacturer. In reference subjects, the 2.5-97.5th percentiles were found to be 4.52-22.33 and 4.84-21.88mg/L for κFLC and λFLC, respectively. The range for κ/λ ratio (0.65-2.36) was validated with the values obtained from subjects with polyclonal hypergammaglobulinemia. In retesting 15 samples from blood donor subjects with a different lot of reagents, mean bias percentages of 17.60 for κFLC and 15.26 for λFLC were obtained. CONCLUSIONS: These findings confirm the lot-to-lot variability of the FLC assays also in the measurement of polyclonal light chains, as well as the need to carefully validate the reference values.

Heterophilic antibody interference in a non-endogenous molecule assay: an apparent elevation in the tacrolimus concentration.

BACKGROUND: In drug monitoring assays the most common interferences are due to hematocrit, other drugs or their metabolites, while the interference by heterophilic antibodies has been reported only when measuring endogenous molecules. In the present paper a heterophilic antibody interference in the tacrolimus measurement is described. METHODS: Samples from a patient treated with tacrolimus were analyzed on RxL Dimension analyzer. Ranging drug concentrations from 49 to 12.5 microg/L, even after the interruption of the treatment, confirmation analysis were performed using heterophilic blocking tubes before tacrolimus measurement on the same analyzer, then testing the samples on V-Twin System, finally incubating the samples with chlorophenol red beta-d-galactopyranoside, beta-galactosidase, polyclonal mouse IgG, protein A and Protein G resin. RESULTS: The elevated tacrolimus concentrations were due to the presence of an interference attributable to heterophilic antibodies, as confirmed by treating the samples with heterophilic blocking tubes and protein G resin. CONCLUSIONS: a) The interference caused by heterophilic antibodies can be found not only in immunoassays measuring endogenous molecules, but also in those for exogenous molecules; b) the pre-treatment sample procedure, which represent the main difference between the methods affected and unaffected by the interference, is a fundamental step in removing the antibodies responsible of the interference.

An expert system for the classification of serum protein electrophoresis patterns.

BACKGROUND: With the improvement of capillary electrophoresis, much progress has been made in terms of sensitivity and automation, but the interpretation of the patterns, actually, depends totally on expert personnel. The aim of this work was to evaluate Neurosoft-Sebia, an expert system developed to discriminate between regular and anomalous serum protein electrophoresis patterns performed on Capillarys2. METHODS: Neurosoft-Sebia, based on six auto-associative neural networks, was trained to create the initial knowledge base. In the tuning phase, 3000 electrophoretic patterns were performed in three different laboratories, and the discordances between human experts and Neurosoft-Sebia classifications were added to the initial knowledge base. Finally, the performances of Neurosoft-Sebia were evaluated using a benchmark dataset. RESULTS: The initial knowledge base was created with 2685 fractions. In the tuning phase, 241 discordances were found: 56 as regular by Neurosoft-Sebia and anomalous by human experts, and 185 as anomalous by Neurosoft-Sebia and regular by human experts. Sensitivity values were evidenced as the ability of Neurosoft-Sebia in selecting anomalous fractions, with an increase from 66.67% using the initial knowledge base to 97.40% using the enriched knowledge base. CONCLUSIONS: This work demonstrated how the ability of Neurosoft-Sebia in selecting anomalous pattern was comparable to that of human experts, saving time and providing rapid and standardized interpretations.

Cystatin C is a more sensitive marker than creatinine for the estimation of GFR in type 2 diabetic patients.

BACKGROUND: Glomerular filtration rate (GFR) is the best overall index of renal function in health and disease. Inulin and 51Cr-EDTA plasma clearances are considered the gold standard methods for estimating GFR. Unfortunately, these methods require specialized technical personnel over a period of several hours and high costs. In clinical practice, serum creatinine is the most widely used index for the noninvasive assessment of GFR. Despite its specificity, serum creatinine demonstrates an inadequate sensitivity, particularly in the early stages of renal impairment. Recently, cystatin C, a low molecular mass plasma protein freely filtered through the glomerulus and almost completely reabsorbed and catabolized by tubular cells, has been proposed as a new and very sensitive serum marker of changes in GFR. This study was designed to test whether serum cystatin C can replace serum creatinine for the early assessment of nephropathy in patients with type 2 diabetes. METHODS: The study was performed on 52 Caucasian type 2 diabetic patients. Patients with an abnormal albumin excretion rate (AER) were carefully examined to rule out non-diabetic renal diseases by ultrasonography, urine bacteriology, microscopic urine analysis, and kidney biopsy. Serum creatinine, serum cystatin C, AER, serum lipids, and glycosylated hemoglobin (HbA1c) were measured. GFR was estimated by the plasma clearance of 51Cr-EDTA. In addition the Cockcroft and Gault formula (Cockcroft and Gault estimated GFR) was calculated. RESULTS: Cystatin C serum concentration progressively increased as GFR decreased. The overall relationship between the reciprocal cystatin C and GFR was significantly stronger (r = 0.84) than those between serum creatinine and GFR (r = 0.65) and between Cockcroft and Gault estimated GFR and GFR (r = 0.70). As GFR decreased from 120 to 20 mL/min/1.73 m2, cystatin C increased more significantly that serum creatinine, giving a stronger signal in comparison to that of creatinine over the range of the measured GFR. The maximum diagnostic accuracy of serum cystatin C (90%) was significantly better than those of serum creatinine (77%) and Cockcroft and Gault estimated GFR (85%) in discriminating between type 2 diabetic patients with normal GFR (>80 mL/min per 1.73 m2) and those with reduced GFR (<80 mL/min/1.73 m2). In particular, the cystatin C cut-off limit of 0.93 mg/L corresponded to a false-positive rate of 7.7% and to a false-negative rate of 1.9%; the serum creatinine cut-off limit of 87.5 micromol/L corresponded to a false-positive rate of 5.8% and to a false-negative rate of 17.0%. CONCLUSIONS: Cystatin C may be considered as an alternative and more accurate serum marker than serum creatinine or the Cockcroft and Gault estimated GFR in discriminating type 2 diabetic patients with reduced GFR from those with normal GFR.