Dickkopf-1 in rheumatoid arthritis: Mechanistic insights, imaging associations, and emerging therapeutic strategies

Table 2 Comparative roles of imaging modalities and dickkopf-1 in rheumatoid arthritis

Parameter	Ultrasound	Radiography	MRI	DKK-1
Detects early synovitis	Yes (PDUS best)	No	Yes	Indirectly
Detects bone marrow edema	No	No	Yes (strongest predictor)	No
Sensitivity in eRA	High	Low	Very high	Moderate-high
Predicts future damage	Yes (persistent PDUS)	Yes (if baseline erosions)	Yes (BME)	Yes (erosions, JSN)
Remission assessment	Subclinical synovitis	No role	Confirms deep remission	Ongoing bone injury risk
Correlation with DKK-1	PDUS: ESR, CRP, DKK-1	RF, ACPA, DKK-1	BME: Erosive risk markers	N/A
Treatment monitoring	Excellent	Poor	Good (costly)	Good; falls with biologics
Key limitation	Operator dependent	Insensitive early disease	Cost and access	Assay variability

ACPA: Anti-citrullinated protein antibodies; BME: Bone marrow edema; CRP: C-reactive protein; DKK-1: Dickkopf-1; eRA: Early rheumatoid arthritis; ESR: Erythrocyte sedimentation rate; JSN: Joint space narrowing; MRI: Magnetic resonance imaging; N/A: Not applicable; PDUS: Power Doppler ultrasound; RF: Rheumatoid factor.