TABLE 1.
Summary of direct and indirect PZA test resultsa
| Parameter | Value for laboratory |
|||||
|---|---|---|---|---|---|---|
| 1 (validation study) | 2 | 3 | 4 | 5 | Total (not including validation study) | |
| No. of patients | 31 | 23 | 13 | 52 | 239 | 327 |
| No. of indirect PZA tests | 31 | 23 | 13 | 37 | 140 | 207 |
| No. of direct PZA tests | 31 | 47 | 13 | 51 | 287 | 398 |
| No. of reportable direct PZA test results/total no. of direct tests done (%) | 24/31 (77.4) | 16/47 (34) | 10/13 (76.9) | 30/51 (58.8) | 179/287 (62.4) | 235/398 (59.0) |
| No. of uninterpretable direct PZA test results/total no. of direct tests done (%) | 7/31 (22.6) | 31/47 (66) | 3/13 (23.1) | 21/51 (41.2) | 108/287 (37.6) | 163/398 (41.0) |
| No. of uninterpretable direct PZA test results/total no. of uninterpretable results (%) caused by: | ||||||
| X200 error (growth failure) | 6/7 (85.7) | 16/31 (51.6) | 2/3 (66.7) | 16/21 (76.2) | 76/108 (70.4) | 110/163 (67.5) |
| Contamination | 1/7 (14.3) | 15/31 (48.4) | 1/3 (33.3) | 5/21 (23.8) | 31/108 (28.7) | 52/163 (31.9) |
| Instrument failure | 1/108 (0.9) | 1/163 (0.6) | ||||
| Direct results | ||||||
| Median time (days) from date of collection to date of start of PZA testing (range) | NA | 0 (0–0) | 1 (0–3) | 0 (0–3) | 2 (0–35) | |
| Median time (days) from date of start of direct PZA testing to date of direct PZA test result (range) | NA | 16 (3–29) | 10 (7–21) | 13 (5–25) | 14 (1–25) | |
| Median time (days) from date of collection to date of PZA test result (range) | NA | 16 (3–29) | 11 (7–21) | 13 (5–25) | 16 (2–49) | |
| Indirect results | ||||||
| Median time (days) from date of collection to date of start of PZA testing (range) | NA | 88 (7–208) | 29 (5–127) | 48 (14–112) | 11 (5–187) | |
| Median time (days) from date of start of indirect PZA testing to date of indirect PZA test result (range)b | NA | 7 (5–13) | 7 (7–14) | 8 (6–16) | 7 (5–19) | |
| Median time (days) from date of collection to date of PZA test result (range) | NA | 95 (14–213) | 40 (12–141) | 59 (21–126) | 18 (11–195) | |
| No. of pairs of direct/indirect results (interpretable results only) | 24 | 10 | 10 | 10 | 109 | 139 |
| No. of pairs in agreement; no. of pairs not in agreement | 24 (17 S, 7 R); 0 | 10 (8 S, 2 R); 0 | 10 (10 S, 0 R); 0 | 9 (9 S, 0 R); 1 (direct R and indirect S) | 105 (97 S, 8 R); 4 (1 direct R and indirect S; 3 direct S and indirect R) | 134 (124 S, 10 R); 5 (2 direct R and indirect S; 3 direct S and indirect R) |
| % agreement | 100 | 100 | 100 | 90.0 | 96.3 | 96.4 |
a
Proportion of reportable direct PZA test results that are either smear negative, scanty, 1+, 2+, or 3+. S, susceptible; R, resistant; NA, not applicable.
b
The difference between the PZA test start date and the PZA test result date does not include the time initially required to obtain a positive culture.