Propositions and strength of recommendation (SOR), ordered according to topic (clinical features, synovial fluid, imaging, comorbidities and risk factors)
| No. | Proposition | LoE | SOR (95% CI) |
|---|---|---|---|
| 1 | Although often asymptomatic, CPPD can present variable clinical phenotypes, most commonly OA with CPPD, acute CPP crystal arthritis and chronic inflammatory arthritis. | IIb | 90 (86 to 94) |
| 2 | The rapid development of severe joint pain, swelling and tenderness that reaches its maximum within 6–24 h, especially with overlying erythema, is highly suggestive of acute crystal inflammation though not specific for acute CPP crystal arthritis. | IV | 88 (84 to 93) |
| 3 | Presentation with features suggesting crystal inflammation involving the knee, wrist or shoulder of a patient over age 65 years is likely to be acute CPP crystal arthritis. The presence of radiographic CC and advanced age increases this likelihood, but definitive diagnosis needs to be crystal proven. | IIb | 81 (74 to 89) |
| 4 | OA with CPPD particularly targets knees with chronic symptoms and/or acute attacks of crystal-induced inflammation. Compared to OA without CPPD, it may associate with more inflammatory symptoms and signs, an atypical distribution (eg, radiocarpal or midcarpal, glenohumeral, hindfoot or midfoot involvement) and prominent cyst and osteophyte formation on radiographs. | Ib/IIb | 53 (38 to 68) |
| 5 | Chronic CPP crystal inflammatory arthritis presents as chronic oligoarthritis or polyarthritis with inflammatory symptoms and signs and occasional systemic upset (with elevation of CRP and ESR); superimposed flares with characteristics of crystal inflammation support this diagnosis. It should be considered in the differential diagnosis of rheumatoid arthritis and other chronic inflammatory joint diseases in older adults. Radiographs may assist diagnosis, but the diagnosis should be crystal proven. | IIb | 83 (72 to 93) |
| 6 | Definitive diagnosis of CPPD is by identification of characteristic CPP crystals (parallelepipedic, predominantly intracellular crystals with absent or weak positive birefringence) in synovial fluid, or occasionally biopsied tissue. | Ib | 94 (90 to 97) |
| 7 | A routine search for CPP (and urate) crystals is recommended in all synovial fluid samples obtained from undiagnosed inflamed joints, especially from knees or wrists of older patients. | IV | 99 (97 to 100) |
| 8 | Radiographic CC supports the diagnosis of CPPD, but its absence does not exclude it. | IIb | 97 (92 to 102) |
| 9 | Ultrasonography can demonstrate CPPD in peripheral joints, appearing typically as thin hyperechoic bands within hyaline cartilage and hyperechoic sparkling spots in fibrocartilage. Sensitivity and specificity appear excellent and possibly better than those of conventional x-rays. | IIb | 78 (70 to 87) |
| 10 | Acute CPP crystal arthritis and sepsis may coexist, so when infection is suspected microbiological investigation should be performed even if CPP crystals and/or CC are identified. | III | 96 (93 to 100) |
| 11 | In patients with CPPD, risk factors and associated comorbidities should be assessed, including OA, prior joint injury, predisposing metabolic disease (including haemochromatosis, primary hyperparathyroidism, hypomagnesaemia) and rare familial predisposition. Metabolic or familial predisposition should particularly be considered in younger patients (<55) and if there is florid polyarticular CC. | Ib/IIb | 94 (89 to 99) |
CC, chondrocalcinosis; CPP, calcium pyrophosphate; CPPD, calcium pyrophosphate deposition; ESR, erythrocyte sedimentation rate; LoE, level of evidence (Ia=meta-analysis of cohort studies, Ib=meta-analysis of case control or cross sectional studies, IIa=cohort study, IIb=case control or cross-sectional studies, III=non-comparative descriptive studies, IV=expert opinion); OA, osteoarthritis; SOR, strength of recommendation on visual analogue scale (0–100 mm, 0=not recommended at all, 100=fully recommended).