TABLE 2.
Performance of diagnostic assays on sputum
| Assay type | No. of positive results/total no. (%)a from sputum of: |
Pb | Pc | ||
|---|---|---|---|---|---|
| Any quality | Good quality | Suboptimal quality | |||
| Culture | 77/229 (33.6) | 21/48 (43.8) | 56/181 (30.9) | 0.19 | 0.10 |
| Gram stain | 51/229 (22.3) | 22/48 (45.8) | 29/181 (16.0) | <0.001 | <0.001 |
| Culture or Gram stain | 105/229 (45.9)d | 30/48 (62.5)e | 75/181 (41.4)f | 0.04 | 0.01 |
| lytA rtPCR | 149/222 (67.1)d | 29/42 (69.1)e | 120/180 (66.7)f | 0.82 | 0.78 |
| lytA rtPCR (highly positive [i.e., CT < 35]) | 116/222 (52.3) | 27/42 (64.3) | 89/180 (49.4) | 0.16 | 0.09 |
a
Positive test denotes growth of pneumococci from culture, visualization of Gram-positive diplococci from Gram stain and detection of lytA by rtPCR, and detection of lytA rtPCR at fewer than 35 cycles (i.e., cycle threshold [CT] < 35), respectively.
b
Comparing good-quality with any-quality sputum.
c
Comparing good-quality with suboptimal-quality sputum.
d
Comparing qualitative lytA rtPCR with either culture or Gram stain (P < 0.001).
e
Comparing qualitative lytA rtPCR with either culture or Gram stain (P = 0.26).
f
Comparing qualitative lytA rtPCR with either culture or Gram stain (P < 0.001).