2 PrioCHECK™ Bovine BVDV Ab Plate Kit Instructions for Use
Conjugate buffer
Dilute reconstituted horse serum 1:20 in dilution working buffer solution;
e.g. for one plate prepare 12 mL (add 0.6 mL reconstituted horse serum to
11.4 mL dilution buffer working solution). The conjugate buffer can be
stored up to 4 hours at 22±3°C.
Conjugate dilution
Dilute Conjugate (30x) (Component 2) 1:30 in conjugate buffer; e.g. for one plate
prepare 12 mL (add 400 µL Conjugate (30x) to 11.6 mL conjugate buffer).
Note: The diluted conjugate must be prepared just before use.
Washing solution
Dilute Washing Fluid (200x) (Component 7) 1:200 in demineralized water.
The amount of Washing Fluid is sufficient to prepare a final volume of
12 liters. Stability of washing solution: 1 week stored at 22±3°C.
Note: Commercially available ELISA washers can be used. If not available,
washing of the plate(s) can be done by dispensing at least 200 µL of
washing fluid to all wells of the plate(s). Subsequently, empty the plate(s)
and repeat as many times as prescribed. It is not necessary to soak the
plate(s) between washings. Tap the plate(s) firmly after the last washing.
Note: See Appendix B for sample preparation procedure and storage.
Incubation of test samples, antigen and conjugate
1. Dispense 100 µL of dilution buffer working solution to the wells
A1 and B1 (= OD450 blank).
2. Dispense 50 µL of the appropriate reference sample to the wells that are
specified in the following table.
Sample type: serum or plasma
Reference Serum 1 (Component 8)
450
Reference Serum 2 (Component 9)
Reference Serum 3 (Component 10)
Sample type: milk (individual or tank)
Reference Milk 1 (Component 11)
450
Reference Milk 2 (Component 12)
3. Dispense 50 µL of the test samples to the remaining wells.
4. Dispense 50 µL of the reconstituted BVDV antigen to all wells except
wells A1 and B1.
5. Cover and shake the Test Plate (Component 1) gently.
6. Incubate the Test Plate for 60±5 minutes at 22±3°C.
7. Empty the Test Plate and wash 6 times with diluted washing fluid. Tap
the plates firmly after the last wash cycle.
8. Dispense 100 µL of the diluted conjugate to all wells.
9. Cover the Test Plate and incubate for 60±5 minutes at 22±3°C.
Incubation with Chromogen (TMB) Substrate
1. Empty the Test Plate and wash 6 times with diluted washing fluid. Tap
the plate firmly after the last wash cycle.
2. Dispense 100 µL of the Chromogen (TMB) Substrate (Component 13) to
all wells.
3. Incubate the Test Plate for 15 minutes at 22±3 °C.
4. Add 100 µL of Stop Solution (Component 14) to all wells.
5. Mix the contents of the wells of the Test Plate.
Note: Start the addition of Stop Solution 15 minutes after the first well was filled
with Chromogen (TMB) Substrate. Add the Stop Solution in the same order and
at the same pace as the Chromogen (TMB) Substrate was dispensed.
Reading of the test and calculating the results
1. Measure the optical density (OD) of the wells at 450 nm within
15 minutes after color development has been stopped.
2. Calculate the mean OD450 of wells A1 and B1 (= OD450 blank).
3. Calculate the corrected OD450 of all samples by subtracting the
mean OD450 blank.
4. Calculate the mean of the corrected OD450 of wells C1 and D1
(= OD450 max).
5. Calculate the percent inhibition (PI) of the reference and test samples
in wells E1 to H12 using the following formula.
The corrected OD450 of all samples is expressed as percent inhibition (PI)
relative to the corrected OD450 max:
PI = 100 − (corrected OD450 test sample / corrected OD450 max) × 100
Result interpretation
Validation criteria
1. The mean OD450 blank (A1 and B1) must be <0.150.
2. The corrected mean OD450 max (wells C1 and D1) must be ≥1.000 for
Reference Serum 1, or ≥0.800 for Reference Milk 1.
3. The percent inhibition of Reference Serum 2 must be >50.
4. The percent inhibition of Reference Serum 3 must be <50.
5. The percent inhibition of Reference Milk 2 must be >30.
Not meeting these criteria is reason to discard the results of that specific test
plate.
Note: If the corrected mean OD450 is below 1.000 possibly the Chromogen
(TMB) Substrate is too cold. In that case pre-warm the solution to 22±3°C or
incubate up to 30 minutes.
Interpretation of the percent inhibition
Serum and plasma samples
PI = <50% Negative
BVDV-specific antibodies are absent in the
test sample.
PI = ≥50% Positive
BVDV-specific antibodies are present in the
test sample.
In case serum or plasma test samples have been titrated, the antibody titre
of a sample is defined as the reciprocal of the highest dilution which gives
PI ≥50%.
A transient BVDV infection is diagnosed when in paired test samples,
collected during the acute phase and more than four weeks later, the
antibody titre changes from undetectable levels to detectable levels or
shows a fourfold rise in antibody titre.
Milk samples
PI = <30% Negative
BVDV-specific antibodies are absent in
the test sample.
PI = ≥30% Positive
BVDV-specific antibodies are present in
the test sample.
Recommended plate layouts
The following plate layouts allow for efficient transfer of pre-diluted samples
and controls to the Test Plate (B — dilution buffer working solution; R1 —
Reference 1; R2 — Reference 2; R3 — Reference 3 (optional); S — Sample).
Table 1 Plate layouts: Test Plate
Appendix A – References
1. Deregt D and Loewen KG (1995). Can Vet J 36:371−378.
2. Kramps JA, Van Maanen C, Van de Wetering G, Stienstra G, Quak S,
Brinkhof J, Ronsholt L, Nylin B (1999). Vet Microbiol Jan. 64(2-3):135−144.
3. Paton DJ, Ibata G, Edwards S, Wensvoort G (1991). J Vir Meth
31:315−324.
Appendix B – Sample preparation procedure and storage
samples should be defatted
by centrifugation for 15 min.
at 1000 × g. Use a pipette to
collect a test sample from
underneath the creamy
layer. As an alternative to
centrifuging the samples
may be kept refrigerated for
at least 16 hours.
• Defatted milk samples can
be stored at −20°C before
• Serum and plasma samples can be
stored at −20°C before testing.
• Serum or plasma samples can be
titrated in the PrioCHECK™ Bovine
BVDV Ab Plate Kit. For this purpose
prepare two-fold serial dilutions (1:10
to 1:1280) in dilution buffer.
• Occasionally, freshly collected serum
and plasma samples may give a weak
false-positive test result. Freezing and
thawing the samples once or by
inactivation at 56°C for 30 minutes