Table 6 Definitions and formulas used for yield calculations
From: High yield of culture-based diagnosis in a TB-endemic setting
Description | Formula | |
|---|---|---|
Ad | Number of SE who had specimens examined | Px + NP + NN + N9 |
Observed # of P SE after 1 specimen | Px | |
Od | Observed # of P SE after 2 specimens | Px + NP |
Sd1 | Fraction of SE found positive on the 1st specimen | Px/(Px + NP + NN + N9) |
Sd2 | Fraction of SE found to be negative on the 1st specimen but positive on the 2nd | NP/(NP + NN + N9) |
Md | # of P SE missed by failing to do a 2nd specimen | Sd2 * N9 |
Expected # of P SE after 1 specimen: same as Observed # of P SE after 1 specimen | ||
Ed | Expected # of P SE after 2 specimens (if all suspects had 2 specimens done) | Od + Md |
Expected proportion of P SE after 1 specimen: same as Sd1 | ||
Rd | Expected proportion of P SE after 2 specimens | Ed/Ad |
Fd1 | Fraction for the potential IY from the 1st specimen | Px / Ed |
Fd2 | Fraction for the potential IY from the 2nd specimen | (Md + NPx) / Ed |
OFP1 | Overall fraction of P on 1st specimen | Rd * Fd1 |
OFP2 | Overall fraction of P on 2nd specimen | Rd * Fd2 |
NND1 | NND on 1st specimen: number of specimens needed to be examined to find one additional case | 1/OFP1 |
NND2 | NND on 2nd specimen | 1/OFP2 |