Factors impacting stimulation assay | Blood collection tubes: within- and between-lot variability |
| Delay in blood processing and incubation time |
| Volume of blood |
Analytical range of readout assay | Limit of detection |
| Lower limit of quantification |
Imprecision of the readout assay | Intra-assay and inter-assay imprecision, in particular around the cut-off for test positivity |
Accuracy of readout assay | Recovery |
Analytical specificity of readout assay | Cross-reactivity |
| Parallelism/dilution linearity |
| Common interferents (e.g. rheumatoid factor, lipids, bilirubin, complement, haemolysate) |
| Evaluation of curve-fitting model (≥5 determinations over multiple runs) |
Additional assessments | Inter-laboratory imprecision (reproducibility) |
| Analyte stability (freeze–thaw stability, short-term bench stability, long-term storage stability) |