Diagnostic Accuracy of Ultrasonography and Conventional Radiography for Calcium Pyrophosphate Deposition Disease Against Crystal-Proven Reference Standards: A Systematic Review and Meta-Analysis

Abstract

Background: Calcium pyrophosphate deposition (CPPD) disease, including acute calcium pyrophosphate (CPP) crystal arthritis (pseudogout), is common in older adults, but synovial fluid crystal analysis is often unavailable, so imaging carries much of the diagnosis.

Objective: To compare the accuracy of ultrasonography and conventional radiography for CPP deposition against a crystal-proven reference standard.

Methods: PubMed, Europe PMC, OpenAlex and Scopus were searched without date or language limits, with citation searching. Studies reporting 2×2 data for ultrasonography or radiography against CPP crystals in synovial fluid or tissue were included. Bivariate random-effects models pooled sensitivity and specificity; bivariate meta-regression compared the tests; QUADAS-2 and GRADE assessed risk of bias and certainty.

Results: Eighteen studies (21 reports) were included. Ultrasonography (15 studies; 1,352 units [participants, knees or menisci], 514 CPP-positive) had a sensitivity of 87.8% (95% CI 79.0–93.2) and specificity of 89.4% (82.2–94.0); radiography (11 studies; 1,053 units) had 52.6% (42.3–62.6) and 96.2% (92.2–98.2). In eight studies applying both tests to the same participants, ultrasonography was 30.4 percentage points more sensitive and 8.2 points less specific (p<0.001 for both). In consecutive patients with effusion or acute arthritis, ultrasonography had 80.8% sensitivity and 89.2% specificity. Certainty was low to moderate.

Conclusion: Against crystal proof, ultrasonography detected most CPP deposition, whereas radiography missed about half but rarely gave false-positive results. Ultrasonography appears to be the more useful first imaging test when crystals cannot be sought; a negative radiograph does not exclude CPPD, and neither test establishes acute CPP crystal arthritis on its own.