Urinary NGAL: Use of absolute value or ratio to creatinine?

Introduction: Neutrophil gelatinase-associated lipocalin (NGAL) has emerged as a promising marker for the detection of acute kidney injury. This marker has been proposed for urinary measurement. However, in the literature, authors indistinctly use "absolute" value or NGAL to creatinine ratio. Up to now, there are no strong arguments favouring for one. This question is of importance as this marker is sensed to be used only on urine random samples. To find an answer to this very practical matter, one approach could be to compare biological CV(intra-individual variation) of the "absolute" and ratio results.