TABLE 2.
Characteristics of the Study Population (Model Development and Validation Subgroups)
| Characteristic | Training Set (n = 250) | Test Set (n = 157) | P |
|---|---|---|---|
| Age at study participation | |||
|
| |||
| Mean (SD), y | 6.1 (4.4) | 6.1 (4.3) | .93 |
|
| |||
| Time from start of maintenance therapy | |||
|
| |||
| Mean (SD), d | 404 (156) | 436 (167) | .053 |
|
| |||
| Race/ethnicity, No. (%) | |||
|
| |||
| Non-Hispanic White | 90 (35) | 53 (35) | .95 |
| Hispanic | 85 (33) | 53 (35) | |
| Asian | 40 (16) | 22 (15) | |
| African American | 42 (16) | 22 (15) | |
|
| |||
| Sex, No. (%) | |||
|
| |||
| Male | 171 (67) | 105 (70) | .47 |
|
| |||
| Age group, No. (%) | |||
|
| |||
| ≥12 y | 47 (18) | 21 (14) | .26 |
|
| |||
| Household income (annual), No. (%) | |||
|
| |||
| <$50,000 (US dollars) | 141 (58) | 85 (60) | .66 |
|
| |||
| Mother as full-time caregiver | |||
|
| |||
| Yes | 118 (47) | 74 (51) | .44 |
|
| |||
| Maternal education, No. (%) | |||
|
| |||
| College graduate or formal training | 138 (55) | 85 (58) | .78 |
| High school plus some college | 31 (12) | 19 (13) | |
| ≤High school | 80 (32) | 42 (29) | |
|
| |||
| Paternal education, No. (%) | |||
|
| |||
| College graduate or formal training | 145 (58) | 88 (62) | .53 |
| High school plus some college | 34 (14) | 14 (10) | |
| ≤High school | 69 (28) | 39 (38) | |
|
| |||
| Household structure, No. (%) | |||
|
| |||
| Nuclear family | 216 (85) | 123 (85) | .88 |
| Single parent/single child | 12 (5) | 8 (6) | |
| Single parent/multiple children | 25 (10) | 14 (10) | |
|
| |||
| NCI risk groups, No. (%) | |||
|
| |||
| High risk | 101 (39) | 59 (40) | .98 |
|
| |||
| Cytogenetics, No. (%) | |||
|
| |||
| Normal | 131 (54) | 64 (45) | .27 |
| Favorable | 101 (41) | 70 (50) | |
| Unfavorable | 12 (5) | 7 (5) | |
|
| |||
| TPMT genotype, No. (%) | |||
|
| |||
| Wild type | 243 (95) | 139 (93) | .44 |
|
| |||
| 6MP ingestion pattern, No. (%) | |||
|
| |||
| Taking 6MP at the same time of day | 172 (67) | 98 (66) | .81 |
|
| |||
| Absolute neutrophil count | |||
|
| |||
| Mean (SD) | 1.99 (1.23) | 2.12 (1.60) | .42 |
|
| |||
| 6MP dose intensity | |||
|
| |||
| Mean (SD) | 0.83 (0.29) | 0.81 (0.26) | .54 |
|
| |||
| Red cell TGN level (pmol/8 x 108 red cells) | |||
|
| |||
| Mean (SD) | 155 (86) | 154 (91) | .92 |
|
| |||
| Mean adherence rates, No. (%) | |||
|
| |||
| <95% | 92 (36) | 56 (37) | .76 |
| <90% | 74 (29) | 41 (27) | .75 |
Abbreviations: 6MP, mercaptopurine; NCI, National Cancer Institute; SD, standard deviation; TGN, thioguanine nucleotide; TPMT, thiopurine methyltransferase.