Cardiac Dysfunction in Duchenne Muscular Dystrophy Is Less Frequent in Patients With Mutations in the Dystrophin Dp116 Coding Region Than in Other Regions.

BACKGROUND: Duchenne muscular dystrophy (DMD), the most common inherited muscular disease in childhood, is caused by dystrophin deficiency because of mutations in the DMD gene. Although DMD is characterized by fatal progressive muscle wasting, cardiomyopathy is the most important nonmuscle symptom threatening the life of patients with DMD. The relationship between cardiac involvement and dystrophin isoforms has not been analyzed. METHODS AND RESULTS: The results of 1109 echocardiograms obtained from 181 Japanese DMD patients with confirmed mutations in the DMD gene were retrospectively analyzed. Patients showed an age-related decline in left ventricular ejection fraction. Patients were divided by patterns of dystrophin isoform deficiency into 5 groups. The cardiac dysfunction-free survival was significantly higher in the group with mutations in the Dp116 coding region than the others, whereas no significant differences in the other 3 groups. At age 25 years, the cardiac dysfunction-free rate was 0.6 in the Dp116 group, but only 0.1 in others. PCR amplification of Dp116 transcript in human cardiac muscle indicated promoter activation. CONCLUSIONS: Left ventricular ejection fraction in DMD declined stepwise with age. Cardiac dysfunction was less frequent in Dp116-deficient than other patients with DMD. Dp116 transcript was identified in human cardiac muscle for the first time. These results indicate that Dp116 is associated with cardiac involvement in DMD.

[Performance Utility of High Sensitivity Quantitative Assay for HBs Antigen].

A high sensitivity quantitative assay for hepatitis B virus (HBV) surface antigen (HBsAg-HQ assay) was recently developed and is useful for earlier detection of HBV reactivation. We created HBsAg-HQ assay operational proce- dures by the sample transport system and laboratory information system. In this study, we evaluated the perfor- mance and utility of the HBsAg-HQ assay based on our operational procedures using internal quality control (IQC) data and 13,762 samples routinely measured for 8 months. The IQC data of the HBsAg-HQ assay demonstrated good accuracy (CV: 1.6-2.7%). The difference in IQC data between two of the same analyzers or several reagent lots had no clinical significance. Of 13,762 samples, HBsAg titer was negative in 12,592(91.5%) and positive in 1,169(8.5%), and HBsAg negative samples were remarkably lower(<0.001 IU/mL) than the cut-off value(0.005 IU/mL). Among 114 HBsAg weakly positive samples ranging from 0.005 to 1.000 IU/mL, false positive results occurred in 12 samples, which were converted into negative results after re-measurement. We could effectively perform carry-over prevention and dilution of high titer samples using our operational procedures. Furthermore, we performed inhibition test in 52 HBsAg weakly positive samples, and 20 samples, most of which were taken from patients with connective tissue disease or malignancy, were judged as non-specific reactivity. Taken together, our operational HBsAg-HQ assay procedures may contribute to efficient workflow for routine testing. Moreover, the HBsAg-HQ assay may be clinically useful for not only highly sensitive assays, but also for reducing false positives.

[Factors Affecting Non-Specific Reaction in Latex Agglutination Turbidimetric Immunoassay for Detection of Matrix Metalloproteinase-3].

PURPOSE: Measurement of matrix metalloproteinase-3(MMP-3), a marker for rheumatoid arthritis, by means of latex agglutination turbidimetric immunoassay (LTIA), has come to replace ELISA kit, but pre-improvement LTIA kit S(Sekisui Medical) frequently shows false values resulting from non-specific reactions. We analyzed factors influencing the frequency of non-specific reactions for MMP-3 detection using various methods. METHOD: Serum MMP-3 levels were measured in 1,214 routine samples or 57 panels with various immunoserological abnormalities by means of pre-improvement and improved kit S, LTIA kit E (Eiken Chemical) and ELISA kit. Non-specific reaction samples were selected either from the routine samples based on the results of correlativity tests between the kits and of dilution linearity tests, or from 57 panels with immunoserological abnormalities based on the results of recovery tests. To explore the factors causing non- specific reactions, titers of rheumatoid factor (RF), immunoglobulins and four heterophil antibodies were measured in these samples. In addition, changes in findings as a result of reduction treatment or IgM absorption were examined in selected samples to clarify the effect of heterophil antibodies. RESULTS: Samples which showed suspected false values probably due to non-specific reaction numbered 75, 15, 5 and 17 as measured with pre-improvement kit S, improved kit S, kit E and ELISA kit, respectively. Kit S also showed high rate of deviation in recovery tests on panels with immunoserological abnormalities. Rate of RF titer in samples with non-specific reactions was higher than that of other factors. Non-specific reaction could be inhibited in two samples as a result of reduction treatment or absorption of IgM subtype. CONCLUSION: Pre-improvement kit S showed a higher rate of non-specific reactions than other kits. The most common cause of non-specific reactions is thought to be high RF titer, but high levels of IgM, including heterophil antibodies, may also affect the values of MMP-3.