Index - 28 - 29 - 30/31 - 32/33/34 - 35 - 36/37/38/39 - 40/41 - 42/43 - 44/45/46 - 47/48 - 49 - 50/51/52/53
54/55 - 56 - 57/58 - 59 - 60/61 - 62 - Pages online: A - B - C - D - E - F - G - References
INDICATIONS AND TESTS FOR PROXIMAL RENAL TUBULOPATHY (PRT)
Indications for proximal renal tubulopathy tests
  • progressive decline in eGFR i
    & eGFR<90 & no other cause and/or
  • confirmed hypophosphatemia ii and/or
  • confirmed increase in UP/C iii
  • renal insufficiency even if stable (eGFR <60)
 Proximal renal tubulopathy tests iv, including
  • tubular proteinuria v
  • blood phosphate and urinary phosphate excretion vi
  • blood glucose and glucosuria
  • serum bicarbonate and urinary pH vii
  • blood uric acid level and urinary uric acid excretion viii
  • serum potassium and urinary potassium excretion

Consider stopping tenofovir if

  • confirmed proximal renal tubulopathy with no other cause
i eGFR: estimated glomerular filtration rate, according to the abbreviated MDRD formula (Modification of Diet in Renal Disease)
ii  Serum phosphate <0.8 mmol/l, or according to local thresholds; consider renal bone disease, particularly if alkaline phosphatase increased from baseline: measure 25(OH) vitamin D, PTH
iii  UP/C in spot urine: urine protein/creatinine ratio in mg/mmol, detects total urinary protein including protein of glomerular or tubular origin. The urine dipstick analysis primarily detects albuminuria as a marker of glomerular disease and  is inadequate to detect tubular disease
iv   it is uncertain which tests discriminate best for tenofovir renal toxicity. Proximal tubulopathy is characterised by: proteinuria, hypophosphataemia, hypokalaemia, hypouricaemia, renal acidosis, glucosuria with normal blood glucose level. Renal insufficiency and polyuria may be associated. Most often only some of those abnormalities are observed.
v   tests for tubular proteinuria include retinol binding protein, α1- or β2 - microglobulinuria, cystatin C, aminoaciduria
vi    quantified as fractional excretion of phosphate (FEPhos): (PO4(urine)/ PO4(serum)) / (Creatinine(urine)/ Creatinine(serum)) in a spot urine sample collected in the morning in fasting state.    
Abnormal >0.2 (>0.1 with serum phosphate <0.8 mmol/L).
vii  serum bicarbonate <21 mmol/L and  urinary pH >5.5  suggests renal tubular acidosis.
viii fractional excretion of uric acid (FEUricAcid): (UricAcid(urine)/ UricAcid(serum) / (Creatinine(urine)/ Creatinine(serum)) in a spot urine sample collected in the morning in fasting state; abnormal >0.1