Table 1.
Performance of Pima™ point-of-care (POC) in measuring CD4+ T-lymphocyte counts as compared to the FACSCalibur™ reference from paired venous and capillary blood of HIV-infected persons by laboratory technicians and lay-counselors in Western Kenya.
| Statistic | Phase I (n = 280) | Phase II (n = 147) | |||||
|---|---|---|---|---|---|---|---|
| Pima Lab Venous CD4 Count | FACS Calibur Capillary CD4 Count | Pima Lab Venous CD4 Count | Pima Lab Capillary CD4 Count | Pima lay-counselors Venous CD4 Count | Pima lay-counselors Capillary CD4 Count | ||
| FACS Calibur Venous CD4 Count | Accuracy (Ca) | 0.990 | 0.993 | 0.982 | 0.953 | 0.915 | 0.941 |
| Precision (r) | 0.932 | 0.968 | 0.960 | 0.963 | 0.954 | 0.958 | |
| CCC (rc) | 0.923 0.903, 0.938 |
0.962 0.947, 0.972 |
0.920 0.904, 0.933 |
0.918 0.893, 0.937 |
0.873 0.838, 0.900 |
0.902 0.873, 0.925 |
|
| Bias (cells/μl, range) | −38.6 −51.5, −25.8 |
−26.9 −37.5, −16.4 |
−65.7 −78.4, −53.0 |
−63.0 −75.3, −50.6 |
−86.4 −100.4, −72.4 |
−71.2 −84.3, −58.2 |
|
| Bias by CD4 Class (cells/μl) | |||||||
| <350 (n = 62) | −4.4 −16.8, 7.9 |
−6.0 −17.7, 5.8 |
−12.2 −25.6, 1.2 |
−6.5 −20.2, 7.1 |
−17.4 −29.7, −5.1 |
−12.7 −24.7, −0.6 |
|
| 350–500 (n = 80) | −18.8 −34.6, −2.9 |
−14.2 −30.6, 2.2 |
−35.1 −54.1, −16.0 |
−35.2 −54.2, −16.2 |
−42.9 −61.6, −24.3 |
−45.2 −65.7, −24.7 |
|
| 500–1000 (n = 115) | −53.4 −73.9, −32.8 |
−29.7 −46.5, −12.9 |
−87.9 −105.2, −70.5 |
−83.6 −99.8, −67.4 |
−118.0 −135.1, −101.0 |
−86.8 −102.7, −70.9 |
|
| >1000 (n = 23) | −126.4 −221.3, −31.6 |
−121.1 −160.8, −81.4 |
−174.2 −249.4, −99.1 |
−184.2 −245.9, −122.5 |
−215.3, −308.4, −122.3 | −235.9 −303.4, −168.3 |
|
| Sensitivity Cutoff (%) | |||||||
| <200 | 95.2 72.9, 99.3 |
100.0 | 88.89 50.01, 98.46 |
100.0 | 100.0 | 100.0 | |
| <350 | 88.7 78.2, 94.5 |
93.6 77.6, 98.4 |
100.0 | 93.6 77.6, 98.4 |
93.6 77.6, 98.4 |
96.8 80.4, 99.6 |
|
| <500 | 93.0 87.4, 96.2 |
93.7 84.3, 97.6 |
96.8 88.2, 99.2 |
98.4 89.6, 99.8 |
100.0 | 98.4 89.6, 99.8 |
|
| Specificity (%) | |||||||
| <200 | 97.7 94.9, 99.0 |
97.8 93.5, 99.3 |
97.8 93.5, 99.3 |
99.3 95.0, 99.9 |
97.1 92.5, 98.9 |
97.1 92.5, 98.9 |
|
| <350 | 89.0 84.1, 92.5 |
94.0 87.9, 97.1 |
92.2 85.8, 95.9 |
97.4 92.3, 99.2 |
94.8 89.0, 97.7 |
93.1 86.8, 96.5 |
|
| <500 | 84.1 77.0, 89.3 |
90.5 82.1, 95.2 |
83.3 73.8, 89.9 |
79.7 69.8, 87.0 |
76.2 66.0, 84.1 |
79.7 69.8, 87.0 |
|
Note for Table 1. ‘n’ refers to paired venous and capillary blood specimens. Bias is expressed in units of cells/μl. Phase I compared the Pima results with FACSCalibur when run by laboratory technicians (denoted ‘Lab’), while Phase II compared results of the Pima device by lay-counselors with those of laboratory technicians.