16:15 Uhr
Auto-Antikörper-Diagnostik in der Diabetologie - Aktueller Stand der Analytik und klinische Anwendung in Deutschland
E. Schleicher (Tübingen, DE)
M. Thaler (München, DE)
Details anzeigen
Autor:innen:
E. Schleicher (Tübingen, DE)
M. Thaler (München, DE)
Autoantibodies against islet cells (IAAB), i.e. autoantibodies against glutamate decarboxylase, insulinoma antigen 2, zinc transporter -8, and insulin, develop early in type 1 diabetes mellitus (DM) when metabolic changes and clinical symptoms are still absent. Presence of IAAB therefore characterizes the first stage of the disease while stage 2 and 3 show dysglycemia and chronic hyperglycemia and overt clinical diabetes, respectively. Being positive years before clinical onset of the disease, IAAB are determined in individuals at high risk for type 1 DM. IAAB are positive in up to 85% of the newly diagnosed patients with type 1 DM indicating that every 6th patient with type 1 DM fails to show IAAB at the time of diagnosis. Novel studies indicate that screening for IAAB in early childhood may predict the disease years before manifestation. In adults, IAAB may serve to classify the DM as type 1 or type 2 / maturity-onset diabetes of the young (MODY) as well as patients as “autoimmune insulin deficient” or “severe insulin deficient”– when clinical and metabolic characteristics are ambiguous. A multitude of methods are employed to determine IAAB in the clinical laboratory. Methods allowing formation of the immune-complexes partially or totally in liquid phase are to be preferred. This is due to the fact that assay formats with solid-phase immobilized antigens seem not to reach sufficient sensitivities and specificities. As with other autoantibodies, comparability of different IAAB assay results is poor. Laboratories are therefore strongly encouraged to establish their own cut-off values in order to enable proper clinical interpretation of the test results. Ring trials for all IAAB mentioned above are currently available in Germany and contribute to analytical quality. Beyond that, the “Islet Autoantibody Standardization Program” as internationally coordinated endeavor aims to improve quality and comparability of IAAB assays.
17:30 Uhr
P-01-10/FV-01:
Critical appraisal of the influence of anti-Thyroglobulin on the measurement of Thyroglobulin and Thyroglobulin recovery
R. Markewitz (Kiel, DE)
Details anzeigen
Autor:innen:
R. Markewitz (Kiel, DE)
K. Wandinger (Kiel, DE)
R. Junker (Kiel, DE)
Background: Antibodies against Thyroglobulin (Anti-Tg) are known to be able to cause interferences in the measurement of Thyroglobulin (Tg). Measuring Tg recovery after adding a known amount of Tg to the sample is a popular method to identify samples that are affected by this interference.
Methods: Results of clinical samples in which Tg, anti-Tg and Tg recovery were measured in a high-throughput clinical laboratory via immunometric assays (by Roche, Switzerland) were retroactively anonymized and analyzed. Specifically, the associations between the analytes Tg, anti-Tg and Tg recovery with one another and with the variables age and sex were statistically evaluated.
Results: 8871 samples were collected, of which only 60 (0.0068%) exhibited pathologically decreased Tg recovery, of which 47 contained quantifiable and 24 pathological levels of anti-Tg. Quantifiable levels of anti-Tg were associated with significantly decreased overall levels of Tg recovery and Tg itself (both: p < 0.0001), with the strongest decreases being associated with pathological levels of anti-Tg. But even for pathological anti-Tg, median Tg-recovery is still well within the reference range at 94±10.4 %. Effect sizes of all detected differences or associations were small to very small.
Conclusion: Tg recovery appears neither sensitive nor specific enough to detect interference of anti-Tg in the measurement of Tg on a single-specimen basis. This interference can nevertheless be detected with statistical methods both for Tg recovery and for Tg itself, albeit with small effect sizes. Methods other than Tg recovery are needed to reliably detect samples with impaired Tg measurement.