ELF score is elevated in patients with recent arthroplasty: a cross-sectional study

The Enhanced Liver Fibrosis (ELF) test is a non-invasive blood test for liver fibrosis, with elevated scores indicating referral to hepatology. However, components of ELF can also be elevated due to extra-hepatic fibrosis after arthroplasty (AP), potentially increasing false positive results. In this study, we investigate whether time since AP is associated with the risk that ELF exceeds clinical thresholds of 9.8 or 11.3. ELF tests were administered to 5,707 Renown Health patients as part of routine clinical care ( N = 1,099) or as part of participating in the Helix Research Network Sub-Study MNASH (HRNSM; N = 4,608). For ELF-tested patients with prior AP, generalized additive logistic regression models were used to assess the association of ELF and ELF components with time since most recent AP. Relative risks (RRs) for elevated values were adjusted for age, sex, HRNSM participation, and ELF testing date. Among ELF-tested patients, we identified 488 patients with prior AP. The RRs of ELF > 9.8 were 1.49 (95% confidence interval [CI]: 1.30, 1.71) and 1.39 (CI: 1.18, 1.63) for patients with AP within 0.5 years prior and AP between 0.5 and 1 years prior, respectively, compared to patients with AP > 2 years prior. Similarly, the RR of ELF > 11.3 was 4.52 (CI: 2.26, 9.02) for patients with AP within 0.5 years. Of the ELF components, procollagen III N-terminal propeptide (PIIINP) contributed the most to elevated ELF scores following AP, with RR 2.32 (CI: 1.93, 2.79) of PIIINP > 9.9 ng/mL for patients with AP within 0.5 years. Compared to patients with AP further in the past, patients with recent AP were significantly more likely to have elevated ELF scores. If extra-hepatic causes are verified, our results indicate that the specificity of ELF for liver fibrosis may be reduced following AP.