Predicting refeeding hypophosphataemia: insulin growth factor 1 (IGF-1) as a diagnostic biochemical marker for clinical practice

Abstract

Background Refeeding syndrome (RS) is a potentially fatal condition that can occur following the re-introduction of nutrition after a period of starvation. Hypophosphataemia following the reintroduction of nutrition is often the only reliable biochemical marker of RS. Refeeding index (RI) generated from baseline insulin-like growth factor-1 (IGF-1) and leptin has been proposed as a useful biochemical marker for the identification of patients at risk of developing refeeding hypophosphataemia (RH). Methods A prospective study included 52 patients referred for parenteral nutrition (PN). The sensitivity and specificity of IGF-1 measured using a sensitive assay was compared to the RI in predicting the development of RH (a ≥30% drop in PO4 during the first 36-h of PN administration). Leptin and IGF-1 were analysed on baseline samples using a quantitative enzyme-linked immunoassay. Daily blood samples were collected from all patients for routine biochemistry for the full duration of PN administration. Results High sensitivity IGF-1 measurement alone was comparable with the RI, using receiver–operating characteristic (ROC) curve analysis, with areas under the curve being 0.79 and 0.80, respectively, and superior to leptin alone (0.72) for predicting ≥30% drop in PO4. The cut-off value for IGF-1 that gave best sensitivity (91% [95% CI 75–98%]) and specificity (65% [95% CI 41–85%]) was 63.7 µg/L, with a likelihood ratio of 2.59. Conclusion Baseline IGF-1 is an objective, sensitive and specific biochemical marker in identifying patients who are at high risk of developing RH prior to PN administration and therefore may have a role in clinical practice.