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BONE DENSITOMETRY (osteoporosis diagnosis)

Dual photon energy (DXA) Discovery QDR densitometer

Dual photon energy is scientifically proven as the most accurate technique for bone density measurement. This device allows spine, femur and wrist density measurements, as well as total body composition (fat). A lateral view of the spine may also be obtained for fracture detection, as well as a bone trabecular score (see hereafter).

From adult age on, bones progressively loose their calcium content throughout life due to excess of urinary waste over assimilation. In women, this loss is stronger after menopause, particularly when menopause occurs early. Other factors are important, such as insufficient exercise, low milk products intake, drugs (prolonged cortisone treatment), family history, etc. Excess bone mineral loss (osteoporosis) may eventually lead to inappropriate and disabling fractures (wrist, spine, femoral neck).

Osteoporosis risk assessment: two tests are proposed hereafter to determine your own risk of osteoporosis:

-The FRAX test (TBS adjusted if available)

- The OST (osteoporosis self-assessment tool) is a simple test for menopaused women, based on age and weight:

Weight (Kg)
Age (years)
50-54
55-59
60-64
65-69
70-74
75-79
80-84
85-89
90-94
95-99
> 99

40-44

O
S
T
E
O
P
O
R
O
S
I S?

45-49












50-54







L





55-59






R


O




60-64







I


W



65-69



M





S




70-74




I





K



75-79





D







80-84

H





D






85-89


I





L





90-94



G





E




95-99




H








Interpretation of your results: if your age/weight profile is located in the red or in the yellow zone of the table, or if you have suffered from a low trauma or atraumatic fracture, you should undergo bone densitometry to look for osteoporosis.

B&D. Uebelhart
Tribune Médicale 37, 09.2004

Geusens P, Hochberg MC, van der Voort DJ et al.
Performance of risk indices for identifying low bone density in postmenopausal women.
Mayo Clin Proc. 2002 Jul;77(7):629-37

When your physician suspects excessive bone loss (osteoporosis), he may decide to perform bone densitometry which estimates the amount of calcium remaining in bone. You will be lying comfortably on a table for about fifteen minutes. During this time, parts of your body (usually femoral neck and lumbar spine) will be scanned by a thin and very low dose x-ray beam composed of two different wavelengths emitted by an electronic tube; by this way one can subtract on successive locations x-ray absorption values corresponding to bone mineral only from data corresponding to small parts plus bone. Densitometry is safe and painless, but it is of course contraindicated in pregnant women.

A density value in g/cm2 is obtained and compared to the mean range of normal values at the same age ad sex; standard deviation (positive or negative) from this range is called z-score; standard deviation from values obtained in young sex matched individuals is called T-score. Osteoporosis as defined by the World Health Organisation is diagnosed when the T-score of the patient exceeds 2.5 negative standard deviations. Beyond this limit fracture risk increases significantly.

densito
Image on next right shows a lateral view of the spine obtained with the densitometer. It allows to look for vertebral body deformation, which increases sensitivity for osteoporosis diagnosis and to detect eventual collapsed lumbar vertebral bodies which should be discarded from spine density measurements.
hip densito
Trabeculometry or trabecular bone score (TBS) is a recently approved method for an more accurate bone fragility assessment. The measurement is obtained from the front spine image of the densitometer. The computer determines the bone trabeculae repartition in the vertebrae to obtain a microarchitecture score. TBS is independant of bone density, allowing adjustment of the FRAX and helping treatment planning. Some persons may have, as a matter of fact, normal bone density values and in the same time show deficient bone microarchitecture, which represents an independant fracture risk. Trabecular bone score

Results will be given to your physician, who will prescribe to you if necessary a calcium-rich diet or even drugs in order to increase or at last stabilise your bone mineral content. More exercise and milk products intake are anyway the first step of treatment. Densitometry may be repeated after one or two years to check treatment efficiency. Reliable follow-up measurements should always be done with the same densitometer and in the same institute, because there are slight calibration differences (baseline definition) between different densitometers.

EXAMPLES OF HIGH CALCIUM CONTAINING FOOD (approximate values):

  • Dairy products
Name
calcium / 100 g (100 ml) - [Magnesium]

Gruyère, Emmental (hard cheese, "swiss cheese")

1150 - [55]

Tilsit, Edam

800

Melt cheese, soft cheese / Mozzarella

550 / 400

Plain milk / Condensed milk

120 / 230 - [13]

Milk chocolate

220 - [47]

Yogurt (fat-free) / Buttermilk

140 / 109 - [14]

White cheese

90

  • Fruit and vegetable

Sesame

780

Hazelnuts / almonds

250 - [160 / 250]

Beer yeast

210

Dried figs

140 - [62]

Soja tofu / Soja seeds

130 / 226

White cabbage / greeen cabbage

180 / 210 - [43]

Spinach, haricot bean / Endive, broccoli

120 - [60] / 100

(Whole bread / Orange)

(50-90 - [90] / 42)

  • Meat and fish

Canned sardines

400

Canned salmon

200

(other meat and fish)

(10-40) - [20]

  • Mineral water (mg/100ml)

Adelbodner / Eptinger / Denner

57 / 56 - [130] / 55

Contrex / Valser

49 - [80] / 44

Aproz / Aquella / Salvega

37 - [70] / 31 / 31

Lostorfer / Cristella / Coop Prix Garantie / Passugger / San Pellegrino

28 / 27 / 25 / 21 / 21 - [60]

Rhäzünser / Badoit / Perrier

20 / 19 / 15

Cristalp / Henniez / Vichy / M-Budget

11 / 11 / 10 / 10 - [2]

Vittel / Evian / Arkina / Volvic

9 / 8 / 4 / 1

Daily calcium intake requirements are 1000 mg in adult age, up to 1500 mg in adolescence, pregnancy and nursing, post-menopausal women and older men and women.

Calcium and urolithiasis: "a low intake of calcium can aggravate the risk of stone formation by increasing absorption and urinary excretion of oxalate", which is the main component of urinary stones (Medical Letter, vol.42 april 3 2000, p. 29-30 / Clin Sci (Colch) 1997 Sep 93:257-63 / J Urol 1998 Mar 159:654-7). Patients suffering from renal stones are therefore advised not to restrict their calcium intake in food. Calcium supplements are likewise not considered a risk factor for urinary stones in healthy persons.

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