Zdeňka Čermáková

Interlaboratory study of free monoclonal immunoglobulin light chain quantification

Abstract Background: Quantification of monoclonal immunoglobulin free light chains (FLCs) in serum is used increasingly in clinical practice for the diagnosis, prognostic assessment, and treatment monitoring of monoclonal gammopathies. It is used as an adjunct to standard serum protein electrophoresis and immunofixation. However, methods for FLC quantification need further standardization and validation. Methods: The Czech Myeloma Group and the Czech Society of Clinical Biochemistry have initiated an interlaboratory study where six laboratories collaborating with the primary myeloma treatment centres measured FLC concentrations in 12 serum samples from patients with monoclonal gammopathies. Results: Repeatability of the measurements in five laboratories was calculated based on differences between the results of duplicate measurements. We found that repeatability depended more on the laboratory than on the device used for measurement. Conclusions: The study revealed several weak points in the methodology, including the need for a uniform sample dilution procedure. Interlaboratory reproducibility was comparable with values achieved in the NEQAS programme. Because the κ/λ ratio cannot be measured with high precision, κ and λ FLC concentrations should be used where possible. Due to its impact on the clinical management of patients with gammopathy, FLC quantification needs to become a part of the regular quality control cycle in myeloma centres.

The New Possibilities in Early Diagnosis of Preeclampsia by Soluble fms-Like Tyrosine Kinase-1 and Placental Growth Factor in 16–20 Weeks Gestation

Background Soluble fms-like tyrosine kinase-1 (sFlt-1) and placental growth factor (PlGF) are used in diagnosing preeclampsia (PE), but their potential in early prediction in pregnant women at 16 to 20 weeks gestation (WG) has remained unexplored. Methods We retrospectively measured serum levels of sFlt-1 and PlGF in 120 pregnant women at 16 to 20 WG. Among these women, 16 had early-onset PE and 23 had late-onset PE. Results Compared with normal pregnancy values, in the serum of women in whom PE later developed, sFlt-1 values increased (P <.001), values of PlGF decreased (P = .001), and the sFlt-1/PlGF ratio increased (P <.001) as early as 16 to 20 WG. Receiver operating characteristic (ROC) curve analysis for the sFlt-1/PlGF ratio at 16 to 20 WG showed an area under the curve (AUC) value of 0.863 (95% confidence interval [CI], 0.788-0.918), P <.001, sensitivity of 74.4%, and specificity of 86.6% for PE in general; and AUC of 0.970 (95% CI, 0.913-0.994), P <.001, sensitivity of 100%, and specificity of 81.5% for early-onset PE only. Also, we determined the 5th and 95th percentiles for sFlt-1, PlGF, and sFlt-1/PlGF ratio values of healthy pregnant women. Conclusion sFlt-1 and PlGF and, in particular, the sFlt-1/PlGF ratio can detect PE as early as 16 to 20 WG-as long as 10 to 15 weeks before PE onset.

Assessment of antibodies against surface and outer membrane proteins of Anaplasma phagocytophilum in Lyme borreliosis and tick-borne encephalitis paediatric patients.

To examine evidence of positive antibodies against immunogenic proteins of Anaplasma phagocytophilum in patients with other tick-borne infections and to diagnose possible co-infections, 412 serum specimens were tested by immunoblotting using three specific Anaplasma antigens: surface proteins p44 and Asp62 and outer membrane protein A (OmpA). In total, 284 serum samples from children with Lyme borreliosis and 12 serum samples from children with tick-borne encephalitis were tested. Sera from patients with viral aseptic meningitis (n = 47) and from blood donors (n = 69) were used as controls. Among all serum specimens from patients with tick-borne infections submitted for this study, six samples (2·0%) showed positive IgM reactions and seven samples (2·4%) were IgG positive for A. phagocytophilum by immunoblot. Borderline reactivity was found in 30 samples (10·14%) for IgM and 36 samples (12·2%) for IgG. The difference between patients and blood donors was statistically significant for IgM (P = 0·006) and for IgG (P = 0·0007) antibodies. A statistically significant result was obtained for IgG (P = 0·02) but not for IgM between patients and children with aseptic meningitis. Immunoblot using three specific antigens provides novel information about the positivity of antibodies to A. phagocytophilum in children with other tick-borne infections. Taking into account clinical and laboratory findings of children despite antibody positivity, no case of human granulocytic anaplasmosis was demonstrated.

Efficient use of basic biochemical methods to prove the presence of monoclonal protein in the clinical diagnosis of malignant monoclonal gammopathy.

Background: This retrospective study evaluates the diagnostic sensitivity of biochemistry methods for the clinical diagnosis of malignant monoclonal gammopathy. In patients with renal insufficiency, renal reference interval as well as standard reference interval is used for evaluating the ratio of free light chains. Methods: We examined samples in 281 patients who were diagnosed with malignant monoclonal gammopathy. The samples were taken at baseline, prior to treatment. Serum and urine protein electrophoresis, serum and urine immunofixation electrophoresis (SIFE+UIFE) and levels of free light chains in serum (FLC) were investigated. Results: Combination of methods with the highest diagnostic sensitivity is the use of maximal number of tests (SIFE+ UIFE + FLC), which identified 98.6% of patients. The achieved results do not statistically significantly differ from the procedure recommended by the International Myeloma Working Group (IMWG) which omitts the urine testing (SIFE + FLC) and identifies 97.9 % of patients (p = 0.523). By using the renal reference ratio of free light chains in patients with renal insufficiency the number of patients identified decreased to the border of significance (p = 0.06) but the number of patients identified by the combination with serum immunofixation (SIFE + FLC) remained the same. Conclusions: The testing algorithm recommended by IMWG for screening patients with the diagnosis of monoclonal gammopathy is effective, diagnostic sensitivity is not significantly lower than the maximal available. Using the renal reference ratio of FLC for evaluation in combination with immunofixation in the serum does not reduce the diagnostic sensitivity of the test and has been reported to increase specificity.