Letter to Physician

Saskatoon Osteoporosis Centre
Dr. W.P. Olszynski, Director

Suite 103, Midtown Medical Centre
39 Twenty-Third Street, East
Saskatoon, Saskatchewan S7K 0H6
(306) 933-2663 Facsimile: (306) 244-6755

Dr. V. Holmes
#301 Midtown Medical Centre
Saskatoon, SK S7K 0H6
Fax: 655-0455

Re: Sunlight Mulitisite Ultrasound

Dear Dr. Holmes:

It is our belief that the Sunlight OmniSense MulitSite (Sunlight US) provides a good tool for fracture risk stratification, in line with what is recommended by Osteoporosis Canada. We do not see the Sunlight US as a diagnostic tool that would replace DXA, but rather as another valid measure of fracture risk that, with clinical judgment, can be added to the patient profile, in combination with well-knows factors such as age, family history of fragility fracture, personal history of fragility fracture and DXA-assessed BMD to correctly assess a given individuals risk for a future fragility fracture.

We have actively used Sunlight Omnisense MultiSite Ultrasound devices (Sunlight US) for over five years in our clinic and have ongoing research projects underway in which the Sunlight US devices are an integral part of our armamentarium for assessing fracture risk. Further, the Canadian MultiSite Osteoporosis Study (CaMOS), the largest Canadian study in osteoporosis with close to 10, 000 participants, uses the Sunlight US for assessing fracture risk. The Sunlight US is a diagnostic device that measures how quickly a generated sound wave propagates across a bony site. The speed that the sound wave travels across the bone has been shown to be proportional to the stiffness of that bone. This stiffness can then be regarded as a crude estimate of bone strength. This ultrasound technology is widely used in both medical and non-medical applications with great result. The Sunlight US is currently the only medical ultrasound device that can measure the speed of sound at a number of bony sites (tibia, phalanx, radius), the others being limited to a single site.

A number of recent scientific articles have investigated the use of Sunlight US in assessing bone strength or fracture risk. An investigation by Hans et el. (1) the Sunlight US was shown to be able to discriminate between those with and without hip fracture, with a 1 SD decrease in speed of sound being associated with a 183 % increased risk for hip fracture. In a study by Nguyen et al. (2), a large cohort of women (549 women, average age of 63 years) were measured by dual-energy x-ray absorptiometry (DXA) at the lumbar spine and femoral neck and by Sunlight US at the distal radius, tibia, and phalanx. Included in the cohort were 77 women with a recent fragility fracture. The distal radius measure was reported to be an independent predictor of fracture risk with a 1 SD loss associated with fracture risk, independent of BMD and age. The combination of QUS and BMD measurements may improve the accuracy of identification of women who will sustain a fracture.” The diagnostic sensitivity in this trial between DXA and the Sunlight US were virtually identical (radial Sunlight US vs. DXA hip BMD).

In our analyses of CaMOS data we have found that there are significant differences in the Sunlight US speed of sound measures between women with and without a vertebral or non-vertebral fracture.

A common misconception is one that Sunlight US is a surrogate measure for DXA, which it is not. In our clinic we have found a wide discordance between the DXA BMD and measures of Sunlight QUS in individual patients. Simply, the sunlight US and the DXA, while both attempting to measure bone resistance to fracture, measure it in different ways. A low BMD will not necessarily lead to a low Sunlight US measure and vice-versa. It is optimal if both devices can be used to assess fracture risk in a patient as there are a large number of women who fracture that would not have been considered an at risk individual when assessed solely by DXA. In this scenario, the Sunlight US may increase the probability that a correct diagnosis is made since it measures different components of bone strength that can strengthen, not replace the use of DXA BMD.

It must be pointed out that Sunlight US is not “QUS calcaneal quantitative ultrasound”, which we agree has been shown to be problematic in the past and has been largely abandoned by scientific and medical communities.

While the use of Sunlight US for assessing fracture risk is notyet widespread, its utility is being abd, has been, demonstrated.

Yours very truly,

W.P. Olszynski, MD., PhD, FRCPC, CCD

WPO/rb

Reference list

(1) Hans D, Genton L, Allaoua S, Pichard C, Slosman DO. Hip fracture discrimination study: QUS of the radius and the calcancum. J Clin Densitom 2003; 6:163-172

(2) Nguyen TV, Center JR, Eisman JA. Bone mineral density-independent association of quantitative ultrasound measurements and fracture risk in women. Osteoporosis Int 2004; 15:942-947