Introduction

The applet below displays gender and ethnic specific curves for bone mineral density for whole body, femoral neck, total hip, and lumbar spine (L2-4). Both areal bone mineral density (BMD) and estimates of volumetric bone mineral apparent density (BMAD) are displayed. BMAD was calculated using bone area and BMC as described (1). These normative data were collected from a convenience sample of 423 healthy American youth (ages 9--25 years) enrolled in a longitudinal study of bone mineral acquisition. Details regarding the study cohort and protocol have been published (1, 2 and 3). The sample included approximately equal numbers of Asian, Hispanic white, non-Hispanic white, and black males and females. Bone mineral was measured by dual energy x-ray absorptiometry (DXA; QDR 1000W, software version 6.1, Hologic Corp., Waltham, MA) in the pencil beam mode. Age and gender specific standard deviation scores (Z-scores) generated at this website apply only to data collected using similar DXA equipment and software. When using these data to interpret scans from other densitometry equipment or software versions, it will be necessary to correct for systematic differences in results as described (4).

References

1. Bhudhikanok GS, Wang M-C, Eckert K, Matkin C, Marcus R, Bachrach LK. Differences in bone mineral in young Asian and Caucasian Americans may reflect differences in bone size. J Bone Miner Res 1996; 11: 1545-1556.
2. Wang M-C, Aguirre M, Bhudhikanok GS, Kendall CG, Kirsch S, Marcus R, Bachrach LK. Bone mass and hip axis length in healthy Asian, black, Hispanic, and white American Youths. J Bone Miner Res 1997 12: 1922-1935.
3. Bachrach LK, Hastie T, Wang M-C, Narasimhan B, Marcus R. Bone Mineral Acquisition in Healthy Asian, Hispanic, Black and Caucasian Youth. A Longitudinal Study. J Clin Endocrinol Metab. In print.
4. Genant HK. Universal standardization for dual x-ray absorptiometry: patient and phantom cross-calibration results. J Bone Miner Res 1995, 10: 997-998.

Disclaimer

Authors

This is joint work of Laura Bachrach, Trevor J. Hastie, and Balasubramanian Narasimhan.

Notes on Applet Use

1. Select the sex, skeletal site, and ethnicity of the subject.
2. To compute the Z-score, enter the age and areal bone density (BMD) or volumetric bone density (BMAD) for the subject in the fields provided and hit Enter. Values outside the expected range will not generate a response. The Z-score will appear in the designated box and the results plotted on the graph.
3. More than one data point can be entered on the same subject by entering the age, BMD or BMAD results, followed by the Enter key. Serial age, bone density, and Z-score data will be listed in the box to the right of the Z-score. Serial data points will be plotted on the graph.
4. Buttons are available to clear all added points, remove a highlighted point in the box, and print.
5. If you wish to compare a number of plots on the same scale, you can use the Options button to fix the x and y axis ranges to desired limits. Pressing the button will pop up a dialog box where you can set the limits among other things.
6. The plots can be (optionally) annotated with a name of a subject. To do this, fill in the fields for the Last Name, Middle Initial and the First Name and hit the Enter key.
7. If you want to generate a report suitable for printing, press the Print button. The result will be a new web page that contains a snapshot of the graph as well as a table of the Z-scores. This page can be printed as usual by using the print button of your browser.

   Printing can be quite slow depending on the speed of your connection, especially with modem connections.

8. To compute Z-score results for additional subjects, press the Clear button and return to step 1 above.

The Applet