The three manufacturers of DEXA equipment do not give STANDARDIZED RESULTS. The differences are clinically important, making it difficult to compare a measurement made from one machine to the other. For example, the hip bone density on a Lunar scan is about 6% higher than on a Hologic scan. If the physician must try to compare studies done on different machines, the best way is to apply the following equations:

TOTAL HIP | |

First Measurement
Hologic Lunar Norland g / cm2 | Second Measurement
Hologic Lunar Norland g / cm2 |

--- mg/cm2 | --- mg/cm2 |

--- % change |

LUMBAR SPINE | |

First Measurement
Hologic Lunar Norland g / cm2 | Second Measurement
Hologic Lunar Norland g / cm2 |

--- mg/cm2 | --- mg/cm2 |

--- % change |

These are the equations:

** sBMD = 1000 (a + b x BMD)**

Manufacturer | Parameter | Femoral neck | Trochanter | Total hip |
---|---|---|---|---|

Hologic | a | 0.019 | -0.017 | 0.006 |

b | 1.087 | 1.105 | 1.008 | |

Lunar | a | -0.023 | -0.042 | -0.031 |

b | 0.939 | 0.949 | 0.979 | |

Norland | a | 0.006 | 0.057 | 0.026 |

b | 0.985 | 0.961 | 1.012 |

**Spine**

- Hologic: 1.0550 (BMD - 0.972) +1.0436
- Lunar: 0.9683 (BMD - 1.100) + 1.0436
- Norland: 0.9743 (BMD - 0.969) + 1.0436

* Using these equations, the average error using standarized BMD for an individual patient was 3.5%.
Reference: Hui, SL, et al. Universal Standardization of Bone Density Measurements: A Method with Optimal Properties for Calibration Among Several Instruments. J Bone Mineral Research 1997;12:1463-70.*