BLT Stages

Abstract Bachelor Project MLT 2018-2019: Analytical and clinical evaluation of ‘Elecsys Active B12’ on the Cobas 6000 Device

Vitamin B12 deficiency is common in mixed patient populations and can cause megaloblastic anemia and irreversible neurological problems. However, there is no single marker which can reliably diagnose B12 deficiency. Furthermore, controversy exists regarding the best diagnostic approach. The aim of this study is to evaluate whether active B12 is a more reliable indicator for vitamin B12 status than total B12. First, this study evaluates the analytical characteristics of the kit ‘Elecsys active B12’. It is found that the intrarun precision, the interrun precision, the bias, the total error and the linearity of the aforementioned kit meets the specified criteria of Ricos and Sciensano. Second, this study investigates the clinical usefulness of active B12 as a first- line screening procedure for vitamin B12 deficiency. Active and total vitamin B12 were measured in eighty-eight serum samples (Cobas 6000; Roche). In the grey zone of active B12 (25-75 pmol/l) and/or total B12 (150-400 ng/l), MMA was tested by LC-MS as a reference marker (> 40,1 µg/l). Critical evaluation of the optimal cut-off values in the grey zones indicates that active B12 (cut-off 50 pmol/l) is not more sensitive than total B12 (cut-off 245 ng/l) (59 % versus 59 %), but the specificity is higher (71 % versus 44 %). Thus, it can be concluded that active B12 has a higher specificity than vitamin B12. The use of active B12 for B12 deficiency, however, is not reliably enough as single marker. Hence, the recommended procedure for testing for vitamin B12 deficiency should start with an active B12 measurement followed by MMA testing in the grey zone. This diagnostic two-step algorithm has the best sensitivity and specificity but is still too expensive to implement.

 

AZ Damiaan Oostende wants to perform the detection of Varicella zoster virus antibodies in-house on the DS2 platform from Dynex®. The aim of this validation is to evaluate two ELISA kits from different companies (EuroImmun and Vircell).

The detection of Varicella zoster virus antibodies is important for several patients. Pregnant women who get in contact with the virus, need to know their immune status for the protection of their unborn child. There are several kits available for detection.  

Different samples were validated and compared on both kits in a short time-frame. Several runs were performed on the DS2 platform with the same samples under the same conditions to compare the results of both kits. The samples were tested for both IgM- and IgG-positivity and compared to the results obtained by the laboratory AML, where these tests were done on a chemiluminescence immunoassay platform. The controls of each run were tracked and compared to each other by calculating mean, standard deviation and coefficient of variation. Specific samples were tested to see if there was any cross-reactivity to Epstein-Barr virus, Herpes simplex virus, Reumafactor and Cytomegalovirus in the detection of IgM-antibodies.

The coefficients of variation were for both IgM and IgG from both kits less than 10%. There was only one sample out of 28 that was discordant for.

The IgM kit from Vircell had significant more cross-reactivity than EuroImmun.

EuroImmun IgM, IgG and Vircell IgM and IgG showed a sensitivity of 100%. The specificity was 100% for EuroImmun IgM, Vircell IgM and IgG. The kit EuroImmun IgG had a specificity of 83,3%.

Due to the lower cross-reactivity and practical considerations, the laboratory chooses to use the IgM/IgG-kits from EuroImmun.