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

Table 1 Correlations between serum dickkopf-1 and indices of disease activity, inflammation, and autoimmunity in rheumatoid arthritis

Parameter	Correlation finding	Ref.
DKK-1 vs DAS-28	r = 0.960 (very strong positive)	Ali et al[9], Juarez et al[54], Fang et al[55]
DKK-1 vs DAS-28 (Spearman)	rho = 0.75	Abdulaziz et al[56], Coras et al[57]
DKK-1 vs CRP	r = 0.640 (significant positive)	Santos et al[11], Sadek et al[42], Coras et al[57]
DKK-1 vs ESR	r = 0.498 (significant positive)	Santos et al[11], Sadek et al[42], Coras et al[57]
DKK-1 vs RF	r = 0.473 (significant positive)	Ali et al[9], Santos et al[11]
DKK-1 vs Anti-CRP antibodies	r = 0.478 (significant positive)	Ali et al[9], Santos et al[11]
DKK-1 vs RA	r = 0.876 (very strong positive)	Santos et al[11]
DKK-1 vs steinbrocker functional grade	Higher levels in class III (4689-8092 pg/mL)	Ma et al[8], Ali et al[9], Sadek et al[42], Juarez et al[54]
Diagnostic cut-off	2726.97 pg/mL; sensitivity of 98.18%, specificity of 100% for active RA by DAS-28	Procaccia et al[58], Bagherzadeh-Fard et al[59], McWilliams et al[60], Pertsinidou et al[61]

DAS-28: Disease activity score 28; CRP: C-reactive protein; ESR: Erythrocyte sedimentation rate; RA: Rheumatoid arthritis; RF: Rheumatoid factor.

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.