Inflammatory low back pain: high negative predictive value of contrast-enhanced color Doppler ultrasound in the detection of inflamed sacroiliac joints.
OBJECTIVE
To determine the value of microbubble contrast agents for color Doppler ultrasound (CDUS) compared with magnetic resonance imaging (MRI) in the detection of active sacroiliitis.


METHODS
An observational case-control study of 103 consecutive patients (206 sacroiliac [SI] joints) with inflammatory low back pain according to the Calin criteria and 30 controls (60 SI joints) without low back pain was conducted at the University Hospital of Innsbruck. All patients and controls underwent unenhanced and contrast-enhanced CDUS and MRI of the SI joints. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of unenhanced and contrast-enhanced CDUS were evaluated.


RESULTS
Forty-three patients (41%) with 70 of 206 SI joints (34%) and none of the controls nor the 60 control SI joints demonstrated active sacroiliitis on MRI. Unenhanced CDUS showed a sensitivity of 17%, a specificity of 96%, a PPV of 65%, and an NPV of 72%; contrast-enhanced CDUS showed a sensitivity of 94%, a specificity of 86%, a PPV of 78%, and an NPV of 97%. Detection of vascularity in the SI joint was increased by contrast administration (P < 0.0001). Clustered receiver operating curve analysis demonstrated that enhanced CDUS (A(z) = 0.89) was significantly better than unenhanced CDUS (A(z) = 0.61) for the diagnosis of active sacroiliitis verified by MRI (P < 0.0001; 2-sided test).


CONCLUSIONS
Microbubble contrast-enhanced CDUS is a sensitive technique with a high NPV for detection of active sacroiliitis compared with MRI.
Klauser
Andrea
A
Innsbruck Medical University, Innsbruck, Austria.
Halpern
Ethan J
EJ
Frauscher
Ferdinand
F
Gvozdic
Dejan
D
Duftner
Christina
C
Springer
Peter
P
Schirmer
Michael
M
D000328:Adult; D000368:Aged; D001168:Arthritis / Q000000981:diagnostic imaging*; D016022:Case-Control Studies; D003287:Contrast Media; D005260:Female; D006801:Humans; D017116:Low Back Pain / Q000000981:diagnostic imaging*; D008279:Magnetic Resonance Imaging; D008297:Male; D045423:Microbubbles; D008875:Middle Aged; D011237:Predictive Value of Tests; D012446:Sacroiliac Joint / Q000000981:diagnostic imaging*; D012680:Sensitivity and Specificity; D018615:Ultrasonography, Doppler, Color / Q000379:methods
D003287:Contrast Media