| 1 | 2 | 3 | 4 | 5* | 6* | 7* | 8* | Total | |
| Test ordering | 25 (15) | 10 (10) | 12 (13) | 18 (28) | 43 (15) | 5 (4) | 7 (10) | 5 (8) | 125 (13) |
| Test implementation | 35 (21) | 19 (19) | 23 (24) | 15 (23) | 28 (10) | 45 (35) | 3 (4) | 5 (8) | 173 (18) |
| Reporting results to clinician | 35 (21) | 31 (31) | 13 (14) | 7 (11) | 89 (32) | 36 (28) | 8 (12) | 19 (29) | 238 (25) |
| Clinician responding to results | 7 (4) | 8 (8) | 9 (10) | 1 (2) | 15 (5) | 9 (7) | 9 (13) | 6 (9) | 64 (7) |
| Notifying the patient of results | 6 (4) | 7 (7) | 7 (7) | 3 (5) | 15 (5) | 6 (5) | 14 (21) | 8 (12) | 66 (7) |
| Administrative | 20 (12) | 9 (9) | 21 (22) | 11 (17) | 49 (18) | 22 (17) | 22 (32) | 16 (24) | 170 (18) |
| Treatments | 5 (3) | 3 (3) | 0 (0) | 1 (2) | 5 (2) | 1 (1) | 2 (3) | 0 (0) | 17 (2) |
| Communications | 13 (8) | 10 (10) | 5 (5) | 4 (6) | 17 (6) | 0 (0) | 2 (3) | 4 (6) | 55 (6) |
| Other process errors | 18 (11) | 2 (2) | 3 (3) | 4 (6) | 17 (6) | 5 (4) | 0 (0) | 3 (5) | 52 (5) |
| Knowledge and skills | 2 (1) | 0 (0) | 2 (2) | 0 (0) | 1 (0) | 0 (0) | 1 (2) | 0 (0) | 6 (1) |
| Total no. of errors for each practice | 166 (100) | 99 (100) | 95 (100) | 64 (100) | 279 (100) | 129 (100) | 68 (100) | 66 (100) | 966 (100) |
| Percentage of errors contributed by each practice | (17) | (10) | (10) | (7) | (29) | (13) | (7) | (7) | (100) |
*Family medicine residency clinics.