BONE DENSITOMETRY Bone density of the proximal femur was measured on men and non-pregnant women aged 20 years and over by a trained examiner in the mobile examination center (MEC). Using dual energy x-ray absorptiometry (DXA), areal bone density (bone mass per unit of area scanned) was measured in five areas of the proximal femur. These were the femoral neck, trochanter, intertrochanter, Ward's Triangle, and total region. Before the exam, screening questions were asked to determine medical safety exclusions. Those excluded from testing were examinees: who were females below age 60 for whom pregnancy test results were positive or uncertain or for whom there was a possibility of pregnancy; for whom both hips had been fractured or broken previously; or who had hip pins or artificial hips. Because these tests were administered in the mobile examination center, the MEC examination sample weight (WTPFEX6) should be used for data analysis. For more information on the use of sample weights in NHANES III data analysis, refer to the NHANES III Analytic and Reporting Guidelines (U.S. DHHS, 1996b). A rigorous quality control program was used throughout the survey to ensure data quality. Quality control (QC) of each individual DXA instrument was monitored by scanning anthropomorphic phantoms on a frequent basis (daily for spine phantom, weekly for hip phantom). Comparability of the three DXA instruments was assessed by circulating an additional spine phantom between mobile examination centers; this "circulating spine phantom" was scanned once per stand. Every anthropomorphic phantom scan was reviewed individually at the Mayo Clinic, and results were plotted to compare with previous QC scan results. All respondent scans also were reviewed individually at the Mayo Clinic before being added to the database. For a detailed description of the QC program and the results for Phase 1 of NHANES III, see the reference by Wahner (1994). QC results for Phase 2 were similar to those for Phase 1. Additional details about the bone density procedure may be found in the references by Looker (1995) and Hologic (1987). Data processing and editing were performed to ensure internal data consistency. Notes have been provided for variables requiring additional explanation. NHANES III Examination Data File ------------------------------------------------------------------------ BONE DENSITOMETRY ------------------------------------------------------------------------ INTRODUCTORY INFORMATION ------------------------------------------------------------------------ Positions Item description SAS name Counts and code Notes ------------------------------------------------------------------------ 5259-5263 Examiner number BDPTECH 15098 01001-09018 1474 88888 Blank but applicable 14739 Blank 5264 Exclusion flag See note BDPEXFLR 16416 0 No exclusion 157 1 Exclusion by protocol 14738 Blank NHANES III Examination Data File ------------------------------------------------------------------------ BONE DENSITOMETRY ------------------------------------------------------------------------ SCAN RESULTS ------------------------------------------------------------------------ Positions Item description SAS name Counts and code Notes ------------------------------------------------------------------------ 5265 Scan was technically acceptable after See note BDPSCAN review at the Mayo Clinic 14646 1 Acceptable scan 321 2 Rejected scan 1449 8 Blank but applicable 14895 Blank 5266 Hip side that was scanned See note BDPSIDE 14501 1 Left hip 145 2 Right hip 1770 8 Blank but applicable 14895 Blank 5267-5270 Bone area of femur neck region BDPFNARE (cm squared) 14646 2.06-7.75 1770 8888 Blank but applicable 14895 Blank 5271-5275 Bone mineral content of femur neck BDPFNBMC region (gm) 14646 00.79-11.58 1770 88888 Blank but applicable 14895 Blank 5276-5280 Bone mineral density of femur neck BDPFNBMD region (gm/cm squared) 17 .000 14629 0.001-0.999 1770 88888 Blank but applicable 14895 Blank 5281-5285 Bone area of trochanter region BDPTRARE (cm squared) 14646 05.35-21.71 1770 88888 Blank but applicable 14895 Blank NHANES III Examination Data File ------------------------------------------------------------------------ BONE DENSITOMETRY ------------------------------------------------------------------------ SCAN RESULTS ------------------------------------------------------------------------ Positions Item description SAS name Counts and code Notes ------------------------------------------------------------------------ 5286-5290 Bone mineral content of trochanter BDPTRBMC region (gm) 14646 02.08-26.36 1770 88888 Blank but applicable 14895 Blank 5291-5295 Bone mineral density of trochanter BDPTRBMD region (gm/cm squared) 7 .000 14639 0.001-0.999 1770 88888 Blank but applicable 14895 Blank 5296-5300 Bone area of intertrochanter region BDPINARE (cm squared) 14646 009.7-39.45 1770 88888 Blank but applicable 14895 Blank 5301-5305 Bone mineral content of intertrochanter BDPINBMC region (gm) 14646 05.19-60.74 1770 88888 Blank but applicable 14895 Blank 5306-5310 Bone mineral density of intertrochanter BDPINBMD region (gm/cm squared) 28 .000 14618 0.001-0.999 1770 88888 Blank but applicable 14895 Blank 5311-5315 Bone area of Ward's triangle region See note BDPWTARE (cm squared) 10 .000 14636 0.005-0.993 1770 88888 Blank but applicable 14895 Blank NHANES III Examination Data File ------------------------------------------------------------------------ BONE DENSITOMETRY ------------------------------------------------------------------------ SCAN RESULTS ------------------------------------------------------------------------ Positions Item description SAS name Counts and code Notes ------------------------------------------------------------------------ 5316-5320 Bone mineral content of Ward's triangle See note BDPWTBMC region (gm) 86 .000 14560 0.001-0.999 1770 88888 Blank but applicable 14895 Blank 5321-5325 Bone mineral density of Ward's triangle See note BDPWTBMD region (gm/cm squared) 4 .000 14642 0.001-0.999 1770 88888 Blank but applicable 14895 Blank 5326-5330 Bone area of total region (cm squared) BDPTOARE 14646 20.41-60.84 1770 88888 Blank but applicable 14895 Blank 5331-5335 Bone mineral content of total region BDPTOBMC (gm) 14646 08.95-89.27 1770 88888 Blank but applicable 14895 Blank 5336-5340 Bone mineral density of total region BDPTOBMD (gm/cm squared) 40 .000 14606 0.001-0.999 1770 88888 Blank but applicable 14895 Blank 5341-5345 K value for scan BDPK 14646 0.174-0.295 1770 88888 Blank but applicable 14895 Blank NHANES III Examination Data File ------------------------------------------------------------------------ BONE DENSITOMETRY ------------------------------------------------------------------------ SCAN RESULTS ------------------------------------------------------------------------ Positions Item description SAS name Counts and code Notes ------------------------------------------------------------------------ 5346-5350 d0 value for scan BDPD0 14646 086.8-136.6 1770 88888 Blank but applicable 14895 Blank NHANES III Examination Data File ------------------------------------------------------------------------ THIS PAGE INTENTIONALLY LEFT BLANK NOTES BDPEXFLR: Exclusion flag This flag variable indicates whether or not the examinee was ineligible to receive the bone densitometry procedure because of known or possible pregnancy or because both right and left hips had been fractured, pinned, or replaced with artificial hip joints in the past. BDPSCAN: Scan technically acceptable after review at the Mayo Clinic See 1994 reference by Wahner for rejection criteria. BDPSIDE: Hip side that was scanned The left hip was chosen as the default side for the bone density scan because it was easier to scan this side given the position of the DXA scanner in the bone density room. If the left hip had been pinned or fractured previously or was artificial, the right hip was scanned. BDPWTARE, BDPWTBMC, BDPWTBMD: Bone mineral area, content, and density of Ward's Triangle region Phases 1 and 2 data for Ward's Triangle are not directly comparable due to a change in the DXA software used to process the data. In Phase 1, the location of Ward's Triangle was variable. The computer algorithm actually searched a specific portion of the femur neck and intertrochanter (2.7 cm x 3.5 cm) for the lowest point of bone mass and then centered a fixed area box (10.5 mm x 10.5 mm)around this point. In Phase 2, however, the location was fixed. The Ward's Triangle position was fixed at a mid-cervical location rather than being the point of lowest bone mineral density. Thus, users should be careful in interpreting observed differences in Ward's Triangle data between Phases 1 and 2. In addition, combining Ward's Triangle data from Phases 1 and 2 may not be appropriate. BDPWTBMC: Bone mineral content of Ward's Triangle See note for BDPWTARE. BDPWTBMD: Bone mineral density of Ward's Triangle See note for BDPWTARE.