T-plus Z-score in the assessment of relative fracture risk.
THE OBJECTIVE OF THE STUDY: We aimed to prove that the relative risk of fractures (RR) is higher in women whose T- and Z-score values come under the category of increased risk than in the women whose T-score only falls within the category of increased risk.


METHODS
We analysed 498 (n=498) densitometric findings from the area of proximal femur: neck (ROI1), Ward's area (ROI2), great trochanter (ROI3) (DXA-dual energy X-ray absorptiometry, Osteocore II, France) from a population of Bratislava women of an average age of 59.71 years <58.63; 60.80>. Measured values of T- and Z-score were categorized as follows: 1--increased fracture risk (T-score<-2.5 SD/T=1, Z-score<or=-1.0 SD/Z=1), 0-without increased fracture risk (T-score>-2.5 SD/T=0, Z-score>-1.0 SD/Z=0).


RESULTS
RR for development of fracture was higher for all measurement sites (ROI(1)-29.87; ROI(2)-15.3; ROI(3)-5.5) for women having T-score<-2.5 SD and simultaneously Z-score<or=-1.0 SD than for the women having T-score<-2.5 SD and simultaneously Z-score>-1.0 SD. When the women were divided according to age into two groups, it was found that the RR of fracture for women<65 years having a T-score<-2.5 SD and also a Z-score<or=-1.0 SD is very high (RR=infinity), elderly women (>or=65 years) had a RR for ROI(1)-32.61, for ROI(2)-7.72, and for ROI(3)-6.9. The probability (P) of the presence of women with T-score values<-2.5 SD and Z-score<or=-1.0 SD in the group under 65 years for ROI1 was 12.5%; for ROI2 34.4%; for ROI3 20.5%, and the probability for women>or=65 years was for ROI1 75%; ROI2 98% and for ROI3 100%.


CONCLUSIONS
The study's contribution lies in the finding that the relative fracture risk of the proximal femur in women increases if the T-score is <-2.5 SD and, simultaneously, the Z-score<or=-1.0 SD, this risk is especially high for women under the age of 65. In assessing the individual fracture risk in female patients we recommend to add also Z-score values in the measured area to T-score values and to other anamnestic and biochemical risk factors.
Wendlová
Jaroslava
J
Osteological Centre, Derer's University Hospital and Policlinic, Bratislava, Slovakia. jwendlova@mail.t-com.sk
D015502:Absorptiometry, Photon / Q000706:statistics & numerical data*; D000367:Age Factors; D000368:Aged; D015519:Bone Density; D015331:Cohort Studies; D005260:Female; D005598:Fractures, Spontaneous / Q000175:diagnosis* / Q000453:epidemiology; D006620:Hip Fractures / Q000175:diagnosis* / Q000453:epidemiology; D006801:Humans; D008403:Mass Screening; D008875:Middle Aged; D015663:Osteoporosis, Postmenopausal / Q000175:diagnosis* / Q000453:epidemiology; D011336:Probability; D012306:Risk; D018154:Slovakia