DLD Hydroxylase Antibody - 21 - Elisa

ASSAY PRINCIPLE 
In RSR’s 21-OH Ab ELISA kit, 21-OH Ab in patients’ sera, reference preparation or calibrators (optional) and controls are allowed to interact with 21-OH coated onto ELISA plate wells. After a 16 - 20 hour incubation, the samples are discarded leaving 21-OH Ab bound to the 21-OH coated on the wells. 21- OH-Biotin is added in a 2nd incubation step where, through the ability of 21-OH Ab to act divalently, a bridge is formed between the 21-OH immobilised on the plate and 21-OH-Biotin.

STORAGE AND PREPARATION OF TEST SERUM SAMPLES 
Sera to be analysed should be assayed soon after separation or stored, preferably in aliquots, at or below –20oC. 100 L is sufficient for one assay (duplicate 50 L determinations). Repeated freeze thawing or increases in storage temperature should be avoided. Do not use lipaemic or haemolysed serum samples. Do not use plasma in the assay. When required, bring test sera to room temperature and mix gently to ensure homogeneity. Centrifuge serum prior to assay (preferably for 5 min at about 10,000 rpm i.e. about 10,000 g in a microfuge) to remove particulate matter. Please do not omit this centrifugation step if sera are cloudy or contain particulates.

CLINICAL EVALUATION 
Clinical Specificity 
Sera from 928 healthy blood donors were tested in the 21-OH Ab ELISA kit. 922 (99.4%) sera were identified as being negative for 21-OH Ab. The remaining 6 (0.6%) of healthy blood donor sera (0.59, 0.93, 1.2, 2.4, >100 and >100 u/mL) were all found to contain IgM antibodies to 21-OH. 

Clinical Sensitivity 
Sera from 100 patients diagnosed with autoimmune Addison’s disease were tested in the 21-OH Ab ELISA kit. 86 (86%) were identified as being positive for 21-OH Ab. 

Lower Detection Limit 
The negative control was assayed 20 times and the mean and standard deviation calculated. The lower detection limit at +2 standard deviations was 0.13 u/mL, the index value was 12.