Letter to the Editor: Comparing the Novel Parameter 'Slope of the Steepest Part of Hemolysis Curve' to Standard Median Corpuscular Fragility for Evaluating Erythrocyte Stability during Prolonged Storage.

OBJECTIVE: Several ways for presenting the results of osmotic fragility test have been described in the literature. Our aim was to compare the utility of a novel parameter for assessment of erythrocyte osmotic properties, i.e., 'Slope of the steepest part of hemolysis curve' with the most frequently used parameter 'Median corpuscular fragility' in order to assess the stability of erythrocytes in a blood sample during prolonged storage. METHODS: Ten whole blood samples were obtained from healthy donors. The osmotic fragility test was initially conducted on the day of venipuncture, and subsequent analyses were carried out on days 1, 2, 4, 7, 9, 11, and 14 after the venipuncture. Mean hemolysis percentage values were used to construct hemolysis curves. The steepest parts of hemolysis curves were estimated to be linear, and lines that overlapped those parts of the curves were created. The slope of these lines was calculated, and the resulting mean values are presented. RESULTS: A significant increase in Median corpuscular fragility values was observed, starting from day of venipuncture. We compared the average values for each day of analysis. The first significant difference in Median corpuscular fragility values was observed on day 4 compared to the day of venipuncture (p=0.006), with values 0.53±0.030 % and 0.41±0.014% respectively. Meanwhile, differences in the values of the slopes of the steepest parts of hemolysis curves were observed as early as day 2 when compared to the day of venipuncture (p=0.046), with values of -966.23±233.07 and -588.01±222.85, respectively. CONCLUSION: Prolonged storage of whole blood samples leads to an increase in osmotic fragility and alters the shape of the hemolysis curve. These changes suggest that postponing the osmotic fragility test could lead to diagnostic inaccuracies. These findings suggest that slope value is a more accurate parameter for evaluating erythrocyte stability during storage, compared to commonly used Median corpuscular fragility value. Hence, it has potential importance and can be complementary to the laboratory result of the OFT. Therefore, it can be useful to provide these results jointly with the results of the OFT test.

Kappa Free Light Chains in Cerebrospinal Fluid of Patients with Identified Oligoclonal Immunoglobulin G.

BACKGROUND: Production of kappa free light chains (KFLC) represents a part of humoral immune response, along with the synthesis of intrathecal immunoglobulins. Increased concentrations of immunoglobulin G light chains, kappa and lambda chains, were identified through research of numerous diseases of central nervous system. The qualitative method of isoelectric focusing (IEF) followed by immunofixation currently represents the accepted standard in identifying oligoclonal bands (OCB), but establishing a sensitive immunonephelometric method for quantification of kappa free light chains (KFLC) in cerebrospinal fluid (CSF) has paved a way for new diagnostic possibilities. Andersson classified the pattern types of OCB, ranging from type 1 to type 5, wherein types 2 and 3 indicate intrathecal synthesis. Our aim was to determine KFLC in CSF of patients with clinically isolated syndrome (CIS) who had presented with type 2 and type 3 OCB, to determine if there is a difference in concentrations between those two groups and to establish a borderline value of KFLC which would enable differential diagnostics. SUBJECTS AND METHODS: 70 patients, who underwent lumbar punction for CSF analysis and had their blood sampled through the cubital vein, participated in the study. Patients were classified according to Andersson as type 2 or type 3, which besides adulthood, represented the inclusion criteria. The average age of patients classified as type 2 was 36 years, and those classified as type 3 was 39 years, where it is evident that there was not a statistically significant difference (p=0.0685). We used a qualitative electrophoretic technique of IEF with agarose gel followed by immunofixation, and a quantitative immunonephelometric method. All results were interpreted on a level of statistic significance of p<0.05. RESULTS: CSF KFLC concentrations in type 3 were statistically and significantly elevated with regard to type 2 (Mann-Whitney test, p=0.0430). The median for KFLC in type 2 was 0.9 mg/L, while the median for KFLC in type 3 was 2.71 mg/L, and the detection limit for both types was 0.18 mg/L. We used a statistical ROC curve to determine that KFLC concentration can be used for differential diagnostics, meaning it can discriminate type 2 from type 3 with clinical sensitivity of 61% and clinical specificity of 71% (AUC=0.641) (p=0.037). CONCLUSION: Despite the obtained statistically significant differences in concentrations of KFLC between types of OCBs and ROC analysis results, determination of KFLC by a nephelometric method, insufficiently strong clinical sensitivity and specificity does not justify abandonment of IEF method followed by immunofixation.