Table 1

Interpretation of IFN results according to the OD ratios obtained with PPD and MIX antigens

PPD
PPD<0.050.05≤PPD<0.3PPD≥0.3
MIX: specific antigens
MIX<0.03NegativeInconclusivePositive
 0.03≤MIX<0.1InconclusivePositive
IF bovine PPD>0.7: positive
 MIX≥0.1
  • Calculation of ratios: ratio PBS=ODPBS/[3×(ODPC−ODNC)], ratio PWM=(ODPWM−ODPBS)/[3×(ODPC−ODNC)], ratio PPD=(ODPPDB−ODPPDA)/[3×(ODPC−ODNC)], ratio PPDB=(ODPPDB−ODPBS)/[3×(ODPC−ODNC)] and ratio MIX=(ODMIX−ODPBS)/[3×(ODPC−ODNC)]. Results were interpreted when ratio PBS<0.125 and ratio PWM >0.2.

  • NC, negative control; OD, optical density; PBS, phosphate-buffered saline; PC, positive control; PPDA, avian PPD; PPDB, bovine PPD; PWM, pokeweed mitogen; with MIX, specific antigens ESAT-6 and CFP-10.