ABSTRACT
BACKGROUND: The presence of oligoclonal IgM bands (OCMB) in cerebrospinal fluid (CSF) is an unfavourable prognostic marker in multiple sclerosis. There is no commercial test to investigate OCMB status. However, a sensitive and specific isoelectrofocusing (IEF) and western blot method was described. We aimed to study the inter-centre reproducibility of this technique, a necessary condition for a reliable test to be incorporated into clinical practice. METHODS: The presence of OCMB was analysed by IEF and western blot with prior reduction of pentameric IgM. We assayed the reproducibility of this test in a blinded multicentre study performed in 13 university hospitals. Paired-CSF and serum samples from 52 neurological patients were assayed at every centre. RESULTS: Global analysis rendered a concordance of 89.8% with a kappa value of 0.71. CONCLUSION: These data indicate that OCMB detection by means of IEF and western blot with IgM reduction shows a good interlaboratory reproducibility and thus can be used in daily clinical setting.
Subject(s)
Immunoglobulin M/cerebrospinal fluid , Blotting, Western , Humans , Limit of Detection , Reproducibility of Results , SpainABSTRACT
An early and accurate diagnosis of multiple sclerosis (MS) is very important, since it allows early treatment initiation, which reduces the activity of the disease. Oligoclonal IgG band (OCGB) detection is a good ancillary tool for MS diagnosis. However, it was argued that its usefulness was limited by the high interlaboratory variability. In the last years, different techniques for OCGB detection have appeared. We performed a blinded aleatorized multicenter study in 19 Spanish hospitals to assess the accuracy and reproducibility of OCGB detection in this new scenario. We studied cerebrospinal fluid (CSF) and serum samples from 114 neurological patients. Every hospital contributed to the study with triplicated pairs of CSF and serum samples of six patients and analyzed 18 different samples. Global analysis rendered a sensitivity of 92.1%, a specificity of 95.1% and a Kappa value of 0.81. This shows that current techniques for OCGB detection have good accuracy and a high interlaboratory reproducibility and thus, represent a good tool for MS diagnosis. When we analyzed separately the different techniques used for OCGB detection, the highest concordance was observed in western blot with alkaline phosphatase detection (kappa=0.91). This indicates that high sensitivity techniques improve the reproducibility of this assay.
Subject(s)
Immunoassay/methods , Immunoglobulin G/analysis , Multiple Sclerosis/diagnosis , Multiple Sclerosis/immunology , Oligoclonal Bands/analysis , Blotting, Western , False Negative Reactions , False Positive Reactions , Humans , Immunoassay/statistics & numerical data , Immunoenzyme Techniques , Immunoglobulin G/blood , Immunoglobulin G/cerebrospinal fluid , Observer Variation , Oligoclonal Bands/blood , Oligoclonal Bands/cerebrospinal fluid , Sensitivity and Specificity , SpainABSTRACT
Single nucleotide polymorphisms (SNPs) in the flanking regions of microsatellite loci (SNPSTRs) help to increase the power of discrimination of short tandem repeat (STR) loci. SNPs are positions in the genome that have been well-conserved over the course of evolution, so analysing them can help distinguish between STR alleles in which the number of repetitions matches due to descent from those which match by chance. This provides support for the determination of biological paternity and other kinship analyses in which mutation needs to be ruled out as grounds for exclusion. Locus D7S820 shows a variable position, SNP rs59186128, in the 5' flanking region. This study is set out (1) to determine the frequencies of SNP rs59186128 in populations with various geographical origins and (2) to estimate the possible contribution of rs59186128 to the allele discrimination of locus D7S820. To that end, individuals from European Caucasoid, Hispanic, and Afro-American populations are studied using denaturing high-performance liquid chromatography, which enables locus rs59186128 to be quickly and highly cost-effectively screened. Moreover, a method is established for determining the haplotypes of SNPSTR rs59186128_D7820. The results show that SNP rs59186128 has a T allele frequency of more than 0.15 in one of the Afro-American populations studied, and the haplotype analysis shows that there is no preferential association between the alleles of SNPSTR rs59186128_D7S820, which supports the idea that they could be useful in forensic applications.
