Paediatric eGFR calculator

You can plot a patient's eGFR over several visits on one chart, and carry the readings forward to their next appointment:

1. Enter the current reading as usual, then click + Add to series (above the result). Repeat this at each visit.
2. Every reading you've added plots together on the chart as a trend line, and lists in the Serial readings panel below the chart, oldest to newest.
3. Click Save readings to file to download a small file containing everything added so far.
4. At the patient's next visit, open the calculator again and click Load readings from file to bring those readings straight back onto the chart.

Readings only exist on your screen and in that saved file — nothing is stored in the browser or sent anywhere, so keep the file the same way you'd keep any other file containing patient information.

The glomerular filtration rate (GFR, mL/min/1.73 m²) is the rate at which the plasma (the water component of blood) is filtered by the kidneys, through their micro-filters or glomeruli. This tells us how quickly the kidneys clean the blood of its waste products.

• The GFR is difficult to measure directly, so in clinical practice it is commonly estimated (eGFR) from the plasma creatinine concentration (Pc). Because creatinine is generated continuously by the body, and excreted by the kidneys, the plasma creatinine rises in a reciprocal fashion as the GFR falls – if the GFR halves, the Pc will double.
• Creatinine is generated in simple skeletal muscle, so after puberty boys and men generally have a higher mean Pc than women.
• Because meat contains creatinine, the Pc may rise briefly after eating a meat meal.
• eGFR values that are derived from Pc must be interpreted with care; GFR may be overestimated in cachectic individuals, and underestimated in more muscular ones, or after a recent meat meal.
• The Pc varies with growth throughout childhood, and with height. The formula used here is designed to allow for these factors when calculating the eGFR.
• Most previous childhood eGFR formulas required you to also know the child’s height, but this one does not.
• If the kidney function falls rapidly, it takes time for the Pc to rise up to reach a new higher concentration plateau. This means there may be a delay in the Pc-derived eGFR demonstrating rapid falls in kidney function.
• Creatinine can be measured by a wide range of methods. In clinical practice, increasingly it is measured by an enzyme method, which is very accurate. However, many laboratories still use the (cheaper) Jaffe method, which also reacts to other chemicals in the blood, so these produce an artificially high result, and the laboratory guesses how much interference there is and subtracts a sum. This makes Jaffe Pc measurements far less reliable.
• Expressed in SI units, creatinine is reported as micromoles per litre, but in historical units it is reported as mg/100 mL. The conversion factor is 1 mg/100 mL = 88.4 µmol/L.