Severity of joint pain and Kellgren-Lawrence grade at baseline are better predictors of joint space narrowing than bone scintigraphy in obese women with knee osteoarthritis.
OBJECTIVE
To compare the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of a baseline late-phase bone scan and assessments of the radiographic and symptomatic severity of knee osteoarthritis (OA) at baseline as predictors of loss of articular cartilage thickness, as reflected in joint space narrowing (JSN) in the medial tibiofemoral compartment.


METHODS
Subjects (174 obese women, 45-64 yrs of age, with unilateral knee OA) were a subset of a larger cohort who participated in a placebo controlled trial of a disease modifying OA drug. Uptake of technetium medronate (99mTc-MDP) in anteroposterior (AP) and lateral views of a late-phase bone scan was measured at baseline in a region of interest drawn around the medial tibia, and was adjusted for (i.e., expressed as a ratio to) uptake in a reference segment of the tibial shaft, which served as an internal standard. Each subject underwent a fluoroscopically standardized radiographic examination of the knees (semiflexed AP view) and a pain assessment with the WOMAC OA Index at baseline, 16 months, and 30 months.


RESULTS
Controlling for baseline joint space width and treatment group, multiple linear regression models showed that the adjusted 99mTc-MDP uptake at baseline was a significant predictor of joint space narrowing (JSN) in the index knee at 16 months (b = 0.180, p = 0.015) and 30 months (b = 0.221, p = 0.049). In the contralateral knee, uptake was only a marginally significant predictor of JSN at 30 months (b = 0.246, p = 0.083). Uptake in the upper and middle tertiles of the distribution predicted subjects who would exhibit JSN >/= 0.50 mm within 16 months with 65% sensitivity (PPV 23%) and 36% specificity (NPV 77%). In contrast, a prediction rule based solely on the presence of Kellgren-Lawrence grade 3 OA severity and greater than median WOMAC Pain score identified progressors with 65% sensitivity (PPV 48%) and 79% specificity (NPV 88%).


CONCLUSIONS
Although the level of adjusted 99mTc-MDP uptake was significantly associated with JSN in knees with established radiographic OA, baseline bone scintigraphy is inferior to the radiographic severity of OA and knee pain (alone or in combination) as a predictor of loss of articular cartilage in subjects with knee OA.
Mazzuca
Steven A
SA
Department of Medicine, Indiana University School of Medicine (IUSM), Indianapolis, 46202, USA. smazzuca@iupui.edu
Brandt
Kenneth D
KD
Schauwecker
Donald S
DS
Katz
Barry P
BP
Meyer
Joan M
JM
Lane
Kathleen A
KA
Bradley
John D
JD
Hugenberg
Steven T
ST
Wolfe
Frederick
F
Moreland
Larry W
LW
Heck
Louis W
LW
Yocum
David E
DE
Schnitzer
Thomas J
TJ
Sharma
Leena
L
Manzi
Susan
S
Oddis
Chester V
CV
D000368:Aged; D018501:Antirheumatic Agents / Q000627:therapeutic use; D018450:Disease Progression; D004318:Doxycycline / Q000627:therapeutic use; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging* / Q000473:pathology; D008875:Middle Aged; D009765:Obesity / Q000150:complications*; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000473:pathology; D010147:Pain Measurement / Q000379:methods*; D011237:Predictive Value of Tests; D011877:Radionuclide Imaging; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D013669:Technetium Tc 99m Medronate; D013977:Tibia / Q000000981:diagnostic imaging
D018501:Antirheumatic Agents; D004318:Doxycycline; D013669:Technetium Tc 99m Medronate