TABLE 4.
Prefortification (1988–1994) |
Early post-fortification (1999–2004) |
Late post-fortification (2005–2010) |
||||
Demographic variable | n | RBC folate | n | RBC folate | n | RBC folate |
nmol/L | nmol/L | nmol/L | ||||
MA | ||||||
Male | ||||||
4–11 y | 810 | 473–1660 | 598 | 667–2180 | 603 | 673–1820 |
12–19 y | 482 | 305–1430 | 1129 | 555–1840 | 628 | 500–1700 |
20–59 y | 1603 | 314–1410 | 948 | 514–1930 | 1041 | 427–1810 |
≥60 y | 504 | 311–1770 | 485 | 527–2730 | 3332 | 534–2320 |
Female | ||||||
4–11 y | 823 | 407–1370 | 587 | 678–2000 | 593 | 667–1800 |
12–19 y | 500 | 318–1480 | 1130 | 575–2100 | 613 | 529–1730 |
20–59 y | 1644 | 318–1670 | 1100 | 560–2310 | 1125 | 501–2250 |
≥60 y | 454 | 319–2070 | 492 | 578–3180 | 3962 | 520–2680 |
NHB | ||||||
Male | ||||||
4–11 y | 756 | 382–1300 | 577 | 642–1550 | 4432 | 572–1610 |
12–19 y | 467 | 234–1140 | 1035 | 471–1380 | 621 | 449–1540 |
20–59 y | 1421 | 246–1160 | 824 | 431–1600 | 968 | 429–1770 |
≥60 y | 470 | 238–1640 | 3402 | 450–2240 | 480 | 449–2660 |
Female | ||||||
4–11 y | 723 | 313–1220 | 576 | 609–1620 | 453 | 594–1490 |
12–19 y | 544 | 218–1120 | 963 | 438–1440 | 566 | 443–1420 |
20–59 y | 1827 | 223–1480 | 930 | 448–1950 | 1089 | 431–1990 |
≥60 y | 487 | 248–1870 | 3742 | 480–2500 | 464 | 442–2400 |
NHW | ||||||
Male | ||||||
4–11 y | 593 | 475–1850 | 471 | 800–2230 | 588 | 688–1930 |
12–19 y | 3272 | 336–1620 | 805 | 577–1920 | 644 | 488–1890 |
20–59 y | 1616 | 326–1710 | 1902 | 600–2320 | 2224 | 540–2190 |
≥60 y | 1381 | 370–2210 | 1343 | 650–3250 | 1535 | 614–3110 |
Female | ||||||
4–11 y | 577 | 462–1620 | 457 | 747–2170 | 534 | 685–1790 |
12–19 y | 4182 | 318–1360 | 802 | 595–2070 | 573 | 540–1910 |
20–59 y | 1930 | 314–1906 | 2142 | 558–2660 | 2361 | 514–2530 |
≥60 y | 1502 | 370–2618 | 1336 | 661–3270 | 1454 | 627–3405 |
Values are reference intervals (2.5–97.5th percentile). RBC folate concentrations were measured by the Bio-Rad radioassay from 1988 to 1994 and from 1999 to 2006 and assay-adjusted to be comparable to the microbiologic assay, which was used from 2007 to 2010 (13, 16, 17). MA, Mexican American; NHB, non-Hispanic black; NHW, non-Hispanic white.
Cell size is smaller than required ( = 448) to estimate the 2.5th and 97.5th percentiles with sufficient precision at an assumed mean design effect of 1.4.