The BÜHLMANN Quantum Blue® Infliximab assay is an immunoassay for the quantitative determination of infliximab trough levels in human serum which can be used to support therapy monitoring. Generally, trough levels in serum that reach a value of 3µg/ml and above correlate well with remission, endoscopic healing of the gut mucosa and low CRP values as well as prediction of sustained response to infliximab therapy.
The test is designed for the selective measurement of infliximab by a sandwich immunoassay. Recombinant tumour necrosis factor alpha (TNFα) is conjugated to gold colloids. On the test cassette the conjugate is released from the pad onto the reastion system as the sample is applied. Infliximab present in the sample will bind to the conjugate. A highly specific monoclonal antibody is immobilised on the test membrane and will capture the conjugate/analyte complex, resulting in a colouring of the test line. The remaining free TNFα/gold conjugate will bind to the control line. The signal intensities of the test line and the control line are measured quantitatively by the BÜHLMANN Quantum Blue® reader.
Specimen Collection and Storage: Collect blood into a plain venipuncture tube without any additives, avoiding hemolysis. Let the serum clot at room temperature for between 20-60 minutes. Centrifuge at room temperature at ~2000g for 15 minutes. Decant the serum. Serum samples can be stored refrigerated at 2-8ºC for up to 3 days and at ≤ -20ºC for at least 3 months.
LF-TLIF10 is read using a second generation Quantum Blue® reader
Sample type: Serum
Sample volume: 10µl
Test time: 15 minutes
Assay range: 0.4-20µg/ml
Below 3µg/ml = low infliximab levels in serum should be used to help the decision to alter the medication, by either dose increase, shortening infusion intervals or a change of drug
Between 3-7µg/ml = trough levels within the therapeutic window can support evidence of effective drug treatment with infliximab, when patients are symptom free
Above 8µg/ml = dose de-escalation to reach the optimal therapeutic window (3-7µg/ml) has no effect on CRP values, Harvey Bradsaw, or Mayo scores on Crohn's or ulcerative colitis patients respectively
Limit of Detection: 0.15µg/ml
Hook Effect: No hook effect was observed up to 1000µg/ml infliximab
Within-Class: No interference was detected with up to 10µg/ml adalimumab, ethanercept and golilimab and up to 1.7µg/ml of certolizumab
Serum Indices: No interference was detected with the following substances up to the stated concentrations:
Triglycerides - intralipid 1320mg/ml; equivalent to 37 mmol/l triglyceride
Conjugated Bilirubin - 342µmol/l; 29mg/dl
Unconjugated Bilirubin - 342µmol/l; 20mg/dl
Haemoglobin - 2g/l; 200mg/dl
TNFα - 2.6ng/ml
Rheumatoid factors - 497.3IU/ml
Immunsuppressive/Co-Medication: No interference was detected with azathioprine (60µmol/l), 6-mercaptopurine (37µmol/l) and methotrexate (1363µmol/l)
Lot specific controls are included within the kit