Elsevier

The American Journal of Medicine

Volume 119, Issue 4, April 2006, Pages 355.e15-355.e24
The American Journal of Medicine

Clinical research study
Diagnostic Performance of 123I-Labeled Serum Amyloid P Component Scintigraphy in Patients with Amyloidosis

https://doi.org/10.1016/j.amjmed.2005.08.043Get rights and content

Abstract

Purpose

To assess the diagnostic accuracy and additional information provided by 123I-labeled serum amyloid P component (SAP) scintigraphy in patients with systemic and localized amyloidosis.

Subjects and methods

123I-labeled human SAP was injected intravenously into 20 controls and 189 consecutive patients with histologically proven amyloidosis: of AA type in 60 cases, AL type in 80, hereditary ATTR type in 27, and localized amyloidosis in 22 cases. SAP scintigrams were obtained 24 hours after tracer injection and were analyzed for abnormal patterns of uptake. Sensitivity and specificity were determined, and scintigraphic findings were compared with clinical data.

Results

Diagnostic sensitivity of SAP scintigraphy for systemic AA, AL, and ATTR amyloidosis was 90%, 90%, and 48% respectively, and specificity was 93%. The distribution of amyloid was less diverse in AA than in AL type. Myocardial uptake was not visualized in any patient. Splenic amyloid was very frequent (80%) in AA and AL type but rarely detected clinically (14%). Abnormal tracer uptake in the liver and kidneys correlated with disturbed liver function and proteinuria, respectively. Bone marrow uptake was specific for AL (21%) and was more frequent in AL kappa than AL lambda. Localized amyloid deposits were not imaged.

Conclusion

SAP scintigraphy is diagnostic of amyloid in most patients with AA and AL type but fewer with hereditary ATTR type, relating to differing distributions and burdens of amyloid in these disorders. It usually reveals more widespread organ involvement than is identified clinically, and certain distributions of amyloid are characteristic of particular fibril types.

Section snippets

Patients

All 219 consecutive patients with histologically proven amyloidosis who were evaluated at Groningen University Hospital, a tertiary referral center, from February 1990 until December 2003 were prospectively screened for the study. Patients were classified to have systemic amyloidosis of the AA, AL, or hereditary ATTR type, or localized amyloidosis.10

Amyloid was diagnosed in all patients by the presence of typical apple-green birefringence in polarized light in a tissue specimen stained with

All Patients

A total of 189 patients were included: 60 with AA, 80 with AL (21 kappa and 59 lambda), and 27 with hereditary ATTR types of systemic amyloidosis, whereas 22 had localized disease. Nineteen patients without amyloid and one healthy person served as controls. Patient characteristics are shown in Table 2.

Positive uptake was seen in 54 AA, 72 AL, and 13 ATTR patients, as shown in Table 3; abnormal images were also obtained in 3 patients with localized disease but in none of the controls. Thus,

Discussion

This study confirms that 123I-SAP scintigraphy is an effective noninvasive tool for diagnosis of systemic AA and AL amyloidosis, which provides additional information on the distribution and amount of amyloid in various visceral sites. Characteristic patterns of organ involvement can give a strong indication of amyloid fibril type, although substantial overlap between types does occur. The sensitivity of SAP scintigraphy is greatest for larger solid viscera, including the spleen, liver and

Acknowledgments

We would like to thank C. Th. Smit Sibinga, W. Tuuk Adriani, P.C. Limburg, and J. Bijzet for manufacturing SAP, and A.K. van Zanten, C. Harms, H. Pol, H. Nijnuis, and J.Boorsma for performing labeling studies and laboratory analysis. The “Dutch Arthritis Foundation” and the “Jan Kornelis de Cock Stichting” provided financial support for this study.

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