Table 1.
Study design, participation, and protocol groups
| Protocol Groupsa | |||||
| Code | Round 1 6/2004 | Round 2 8/2004 | Round 3 12/2004 | # | |
| 1A | A | 1 | |||
| 1B | B | B | 2 | ||
| 2 | B | B | 2 | ||
| 3 | A | A | 2 | ||
| 4 | C | C | C | 3 | |
| 5 | A | A | A | 3 | |
| 6 | A | A | A | 3 | |
| 7 | A | A | A | 3 | |
| 8 | C | C | C | 3 | |
| 9 | C | C | C | 3 | |
| 10 | Y | 1 | |||
| 11 | A | A | 2 | ||
| 12 | B | B | B | 3 | |
| 13 | A | A | 2 | ||
| 14 | A | A | A | 3 | |
| 15 | A | A | 2 | ||
| 16 | A | A | A | 3 | |
| 17 | B | B | 2 | ||
| 18 | Z | 1 | |||
| Total | 19 | 13 | 16 | 15 | 44 |
a) Four measurement protocol groups, "A" to "C", were identified on the basis of common suppliers of enzymes, purification kits, instrumentation and similar operating conditions. Two participants used unique protocols that are coded "Y" and "Z".