Table 4. Comparison of Number of sputum samples required to detect one additional TB case on 2nd and 3rd sputum culture versus TB expert critical values.
| Culture method | First sample culture (spot specimen)n (95% CI)a | Second sample culture (morning specimen)n (95% CI)b | Expert opinion on2nd sample culture | Third sample culture (spot specimen)n (95% CI)c | Expert opinion on3rd sample culture |
| LJ alone | 4.7 (3.7–6.7) | 29.9 (16.6–156.5) | 21, 32,3, 104, 12 µ 5 | 55.6 (26.4–500.4) | 32,3, 51, 17 µ 5 |
| MGIT alone | 3.9 (3.1–5.2) | 11.3 (7.6–21.9) | 21, 32,3, 104, 12 µ 5 | 35.7 (19.0–313.8) | 32,3, 51, 17 µ 5 |
| LJ plus MGIT | 3.3 (2.7–4.2) | 20.8 (12.5–62.7) | 21, 32,3, 104, 12 µ 5 | 36.1 (19.1–330.9) | 32,3, 51, 17 µ 5 |
LJ (Solid culture) = Lowenstein Jensen, MGIT (Liquid culture) = Mycobacterium Growth Indicator Tube.
1
Derek Armstrong, 2Richard Oatis, 3John Kenneth 4∼Armand Van Deun, 5Nicole Parrish;
Order has no superiority meaning.
∼ = the third sample was not necessary and could not recommend for it to be examined.
CI = Confidence Interval.
a
= 1/Px*170, b = 1/NPx +positive missed by second*170 and c = 1/NNP + positive missed by third * 170, µ = Expert opinion Critical value for the second and third sputum sample culture.