Assay of Factor VIII Antibodies by ELISA Using Plasma Specimens Dried On Filter Paper and Stored at Room Temperature.
Bibliographic record
Abstract
Abstract Abstract 3479 Poster Board III-416 Introduction ELISA assays have been proposed as a complement to the Bethesda assay for detection and follow-up of factor VIII (FVIII) antibodies in subjects with hemophilia. The Bethesda assay has several drawbacks. Most importantly, the Bethesda assay would not detect non-inhibitory antibodies, even though these could be responsible for low in vivo recovery of FVIII and /or a pharmacokinetic pattern suggestive of rapid clearance of FVIII. ELISA assays for detecting antibodies to FVIII are not routinely performed in most hospital laboratories and as such, specimens need to be transported to specialized laboratories for processing. Transportation of plasma specimens frozen on dry ice, however, is both costly and cumbersome. Room temperature storage of whole blood and serum specimens adsorbed and dried onto filter paper has been shown to be a convenient and reliable alternative to frozen whole blood and serum samples for various analyses. This study was undertaken to assess whether FVIII antibodies from haemophilic plasma would display similar stability when stored adsorbed onto filter paper at room temperature for 1 month or on plasma specimens stored frozen. Stability was assessed by comparing results of ELISA assays. Methods two hundred and thirteen frozen (at -80°C) plasma samples from patients with or without known FVIII inhibitors were tested. Samples came from 97 congenital haemophilic subjects and 5 subjects with acquired haemophilia. The samples were tested with a previously reported ELISA assay (Haemophilia 2009; 15: 374-6) with minor modifications. The coating antigens were two therapeutic preparations of recombinant FVIII: the full length FVIII preparation Helixate® FS, and the B-domain deleted FVIII Xyntha®. Five dilutions of plasma from a subject with congenital severe hemophilia A known to have a high Bethesda titer was put on all plates as positive control. Six normal plasmas were used on all plates as negative controls. Mean and standard deviation of optical densities were calculated for negative controls. Mean was subtracted from optical density of each test plasma. The resulting value was divided by the value of one standard deviation of negative controls to generate the number of standard deviations for test plasmas. All plasmas were assayed in duplicate. The numbers of standard deviations were compared between frozen samples and samples dried on filter papers. Results The correlation between the numbers of standard deviations obtained with frozen specimens and with specimens dried on filter paper was excellent for both therapeutic preparations of recombinant FVIII, going from R= 0.91 to R= 0.99. Conclusion FVIII antibodies tested by ELISA using plasma dried on filter paper for one month at room temperature or plasma stored at -80°C give comparable results. Disclosures: No relevant conflicts of interest to declare.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.010 | 0.006 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".