In keeping with these international guidelines, Ampath has decided to start reporting eGFR together with serum creatinine. As this involves only a calculation, it is reported free of charge. We are going to use the MDRD-formula for calculation. This formula was derived from the Modification of Diet in Renal Disease (MDRD) Study, and takes into account the patient’s age, gender and ethnicity. Because the black population have relatively high serum creatinine concentrations compared with Caucasians, a corrective factor needs to be applied to their results. There is limited published evidence on the applicability of the formula to South Asians, Chinese or other ethnic groups, and until such evidence becomes available, it is probably reasonable to assume no correction for ethnicity in these latter groups. Patient weight or height is not required because the formula normalizes results to a standard body surface area (BSA) of 1.73 m2.

* Diagnosis of stage 1 and 2 CKD requires additional/alternative evidence of kidney damage eg microalbuminuria or proteinuria.

There are certain limitations to the use of formulaestimated GFR, including:

• Result should be multiplied by 1.212 in black
  population.
• eGFR between 60 and 89 mL/min/1.73 m2 may
  indicate mild renal function impairment only in
  the presence of microalbuminuria or proteinuria,
  which is of clinical significance for patients
  with hypertension and/or diabetes.
• eGFR is unreliable at the extremes of body size
  and age.
• eGFR underestimates GFR in cases of mildly
  reduced, normal and increased (eg. early DM/
  pregnancy) renal function.
• eGFR is unreliable in acute renal failure.

The following clinical situations require more precise knowledge of GFR, and reliance on formula-based estimates of GFR only should be avoided:

• Use of chemotherapy or other drugs with narrow therapeutic margin.
• Assessment of kidney donors.
• Muscle wasting disorders, eg paraplegia.

Despite the major limitations of using formulaestimated GFR’s, it will still improve the recognition and subsequent management of chronic kidney disease, compared with use of serum creatinine alone.

For further information, contact:
Drs JC Senekal, L van Niekerk, H Rossouw,
M du Plessis: (012) 427 1800

Berekende glomerulêre filtrasie spoed
(eGFS)
(berekende kreatinienopruiming):
Verduideliking, interpretasie en beperkings

In ooreenstemming met hierdie internasionale riglyne gaan Ampath voortaan die berekende eGFS saam met serum kreatinien rapporteer. Aangesien die eGFS ’n berekening is, is daar geen koste aan verbonde nie. Ons gaan van die MDRD-formule gebruik maak. Hierdie formule is afgelei van die“Modification of Diet in Renal Disease (MDRD) Study” en neem die pasiënt se ouderdom, geslag en etnisiteit in ag. Aangesien die swart bevolking se serum kreatinien relatief hoër is in vergelyking met kaukasiërs, moet hulle resultate aangepas word met behulp van ‘n korreksiefaktor. Vir Suid-Asiërs, Chinese en ander etniese groepe is voldoende inligting oor die toepaslikheid van die formule nog nie beskikbaar nie, en intussen kan aanvaar word dat korreksie vir ander etniese groepe nie nodig is nie. Die pasiënt se massa en lengte word nie benodig nie, aangesien die formule resultate normaliseer na ’n standaard liggaamsoppervlak area (BSA) van 1.73 m2.

Classification of chronic kidney disease (CKD) (adapted from National Kidney Foundation)
Stage	GFR	Description
1*	> 90	Kidney damage with normal/increased GFR
2*	60-89	Kidney damage with mildly decreased GFR
3	30-59	Moderately decreased GFR
4	15-29	Severely decreased GFR
5	< 15	Kidney failure

• Resultate van swart pasiënte moet met 1.212 vermenigvuldig word.
• ‘n eGFS van 60 – 89 mL/min/1.73m2 kan moontlik dui op geringe nierfunksie-inkorting in die teenwoordigheid van ander kenmerke van nierskade soos mikroalbumienurie of
  proteïenurie, wat klinies betekenisvol is vir pasiënte met hipertensie en/of diabetes.
• eGFS is onbetroubaar by die uiterstes vanliggaamsgrootte of ouderdom.
• eGFS onderskat GFS in geval van gering verlaagde, normale en verhoogde (bv. vroeë
  DM/swangerskap) nierfunksie. eGFS is onbetroubaar met akute nierversaking.

Sommige kliniese situasies vereis meer akkurate bepaling van GFS en daarom word die gebruik van formule-gebaseerde bepaling van GFS alleenlik, afgeraai:

• Behandeling met chemoterapeutiese of ander middels met ’n nou terapeutiese venster.
• Evaluasie van potensiële nierskenkers.
• Siektes wat spieratrofie veroorsaak, bv paraplegie.

Ondanks die genoemde beperkinge, sal die gebruik van die berekende GFS lei tot vroeër diagnose en effektiewe behandeling van chroniese niersiekte, in teenstelling met die gebruik van serum kreatinien alleenlik.

Vir meer inligting kontak:
Drs JC Senekal, L van Niekerk, H Rossouw,
M du Plessis: (012) 427 1800