Table 3.
Urine biochemistry
| Reference | Test | Patients (n) |
AUC | Sensitivity (%) |
Specificity (%) |
PPV (%) |
NPV (%) |
Comments |
|---|---|---|---|---|---|---|---|---|
| Carvounis89 | FeU vs. FENa | 102 | 90 | 96 | 99 | 75 | Gold standard clinical grounds; more sensitive and specific index than FENa in differentiating between ARF due to prerenal azotemia and that due to ATN, especially if diuretics have been administered; in osmotic diuresis, the proximal tubular absorption of salt and water is impaired; thus, increased FEUN is expected despite renal hypoperfusion. A similar picture emerges in patients given a high protein diet or having excessive catabolism. | |
| PR = 50 | ||||||||
| Prdiu = 27 | ||||||||
| ATN = 25 | ||||||||
|
| ||||||||
| Pepin90 | FeNA vs. Feur in transient AKI (prerenal) | 99 | Gold standard clinical context and whether serum creatinine level returned to baseline within 7 days. In patients without diuretic use, FENa is better able to distinguish transient from persistent AKI. In patients administered diuretics, this distinction cannot be made accurately by means of FENa. FEur cannot be used as an alternative tool because it lacks specificity. | |||||
| FENa | 0.83 ± 0.07 | 78 | 75 | 86 | 64 | |||
| FENA + dir | 0.75 ± 0.06 | 68 | 81 | 86 | 49 | |||
| FEur | 0.56 ±0.11 | 48 | 75 | 79 | 43 | |||
| FEur + diur | 0.57 ± 0.08 | 79 | 33 | 71 | 44 | |||
|
| ||||||||
| Bagshaw86 | FeU ≤35% | n = 28 | 0.54 (0.42–0.67) | 40 | 59 | Gold standard: uNGAL. In sepsis, FeNa and FEUN are not reliable markers of renal hypoperfusion. Urine biochemical profiles and microscopy do not discriminate septic and non-septic AKI. UNa, FeNa, and FeU do not reliably predict biomarker release, worsening AKI, RRT or mortality. These data imply limited utility for these measures in clinical practice in critically ill patients | ||
| FeNa <1% | n = 47 | 0.54 (0.42–0.67) | 50 | 58 | ||||
AKI, acute kidney injury; ARF, acute renal failure; ATN, acute tubular necrosis; AUC, area under the curve; diur, diuretics; FENa, fractional excretion of sodium; FeU, fractional excretion of urea; FEUN, fractional excretion of urea nitrogen; NPV, negative predictive value; PPV, positive predictive value; RRT, renal replacement therapy; UNa, urine sodium; uNGAL, urine neutrophil gelatinase-associated lipocalin.