La Ashley M., Gunning Samantha, Trevino Sharon A., Kunczt Alissa, Forni Lui G., Swamy Varsha, Zarbock Alexander, Groboske Sarah, Leung Edward K.Y., Yeo Kiang-Teck J., Koyner Jay L.: Real-World Use of AKI Biomarkers: A Quality Improvement Project Using Urinary Tissue Inhibitor Metalloprotease-2 and Insulin-Like Growth Factor Binding Protein 7 ([TIMP-2]*[IGFBP7]). American Journal of Nephrology DOI 10.1159/000531641
Novel urinary biomarkers for the early prediction of AKI in newly admitted patients to intensive care units (ICU) have been developed, but the overall clinical utility of these tests and the timing of their use remain uncertain.
La and co-workers carried out a single-center, prospective, observational study of patients admitted to the ICU who were at risk of developing severe AKI (KDIGO Stage 2/3). Treating physicians were allowed to test patients with urinary tissue inhibitor metalloproteinase-2 and insulin-like growth factor binding protein 7 (TIMP-2*IGFBP7) by commercially available point-of-care methods. Historical controls not tested were used as comparators.
The 7-day progression to severe AKI when TIMP-2*IGFP7 levels were >0.3 was 28% in the prospective cohort and 21% in the historical cohort (p = 0.38), but Stage 1 CKD was present at the time of testing in 67% of the prospective cohort and in 23% of the historical controls (p < 0.001). Patients with elevated TIMP-2*IGFBP7 were more likely to receive a nephrology consult, and early nephrology consultation was associated with better volume control, less severe AKI, and lower dialysis requirement compared to historical controls.
While this study is not conventionally randomized and controlled, it does resemble a “real-life” scenario, at least in reference to a single-center experience. These limitations lead to confounding by unmeasured variables and bias of some relevance. Also, unlike many other reports of the utility of biomarker testing, many of the patients in the prospective cohort already had Stage 1 AKI at the time of testing. With findings of TIMP-2*IGFBP7 of >0.3–2.0 versus <0.3, the overall risk of progression was not greatly different. However, under the “watchful eye” of a nephrology consultant (triggered by a TIMP-2*IGFBP7 >0.3), the outcomes of Stage 1 AKI seemed to be better. One might ask whether a nephrology consult should be regularly recommended for Stage 1 AKI, independent of biomarker testing. More research is needed in patients admitted to the ICU and at risk for AKI (e.g., sepsis, trauma, elderly, etc.) to determine if routine testing for urinary AKI biomarkers adds benefit in terms of outcome in the presence of universal nephrology consultation for stage 1 AKI.