I am doing indirect Elisa with test serum sample and negative serum samples. Someone please let me know how to calculate the cut-off value to determine the titre.
For diagnostic assays its usually recommended to have a panel of both negative and positive samples and to use statistic methods to determine the cut-off value providing the best discrimination between them. Specificity and sensitivity of the assay can be fine-tuned depending on the requirements of the diagnostic application. If there are good and relatively simple confirmatory tests, perhaps its better to have false-positives (that can be subsequently confirmed or not) in order to avoid loosing any positive individuals...Other cases can be different.
During routine sera evaluation for research purposes, for instance to do titrations affter immunization, its common that the researcher sets a cut-off by taking into account the background levels of the assay (either without sera or with sera that is known to be negative). Some researchers take 2- or 3-fold the average background levels as the cut-off to be very stringent in considering something positive, while others calculate the mean value + 2- or 3-SD for the negative wells and take this as the cut-off.
What is important is to use a uniform criteria during a given study.
For diagnostic assays its usually recommended to have a panel of both negative and positive samples and to use statistic methods to determine the cut-off value providing the best discrimination between them. Specificity and sensitivity of the assay can be fine-tuned depending on the requirements of the diagnostic application. If there are good and relatively simple confirmatory tests, perhaps its better to have false-positives (that can be subsequently confirmed or not) in order to avoid loosing any positive individuals...Other cases can be different.
During routine sera evaluation for research purposes, for instance to do titrations affter immunization, its common that the researcher sets a cut-off by taking into account the background levels of the assay (either without sera or with sera that is known to be negative). Some researchers take 2- or 3-fold the average background levels as the cut-off to be very stringent in considering something positive, while others calculate the mean value + 2- or 3-SD for the negative wells and take this as the cut-off.
What is important is to use a uniform criteria during a given study.
- Badges
- Science method
- Similar topics
- Medicine
- Immunology
- Immunology Techniques
- Immunoassay
- ELISA