Sensitivity Threshold
Definition
The smallest stain on which a technique still gives a reliable read. The key axis for choosing between Lattes, inhibition, elution and mixed agglutination.
- Definition
- Smallest stain size giving a reliable read
- Governs choice among
- Lattes, inhibition, elution, mixed agglutination
- Field
- ABO blood group typing from bloodstains
- Practical impact
- Determines the minimum sample size a lab will attempt
- Trade-off
- Higher sensitivity methods often need more careful control testing
Common questions
Why would a lab choose the elution method over the Lattes method for a small stain?+
The absorption-elution method is generally more sensitive and can type smaller or more degraded stains than the older Lattes technique, which needs a comparatively larger, better-preserved sample to release a readable agglutination pattern.
Does a lower sensitivity threshold always mean a better test?+
Not necessarily. A more sensitive method can also be more prone to weak or ambiguous reactions on marginal samples, so labs weigh sensitivity against specificity and the reliability of the read, not sensitivity alone, when selecting a technique.
Why has ABO grouping from bloodstains become less common in casework?+
DNA profiling now provides far greater individualising power from the same or smaller stains, so ABO group typing, once the primary bloodstain individualisation method, is largely reserved for historic casework or contexts where DNA testing is unavailable.
Related terms
- Absorption-Elution
- A technique for detecting antigens on dried red cell debris. Specific antiserum is absorbed onto the stain; if the antigen is present,...
- Absorption-Inhibition
- A known volume of antiserum is exposed to the stain; the residual unbound antibody is then titrated against indicator cells. A drop...
- Agglutination
- Clumping of red cells that occurs when antibodies in serum bind to incompatible antigens on the cell surface, cross-linking cells into visible...
- Antiserum
- Serum collected from an immunised animal containing antibodies directed against a specific antigen or group of antigens. In species identification, antiserum raised...
- Lattes Crust Method
- Classical direct agglutination. A crumb of the dried crust is teased into a drop of known antiserum on a slide. Leone Lattes,...
- Mixed Agglutination
- A microscopy-based technique in which indicator cells form rosette aggregates around antigen-bearing stain material via antibody bridges. Positive results are read as...
- Secretor Status
- A genetic trait that determines whether a person expresses their ABO blood group antigens in secreted body fluids such as saliva, semen,...