How to Apply GFR Formula? #791
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Dear to all, |
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Replies: 10 comments 7 replies
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@StephanSchaller, |
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I was only tagging another OSP community member (Jan Schlender) to prompt him to answer to this question as he is quite the expert on renal clearance in PK-Sim ;-) |
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I am attaching the full equation for specific GFR in PK-Sim. Specific GFR (mL/min/100g kidney) is then multiplied out by the individual's kidney volume to get the individual GFR (mL/min). Be aware that the GFR would then need to be standardized by the individual BSA if comparing to clinical measurements, which are reported in units of mL/min/1.73m2. The hill function for aging does not apply when age is less than 30. There is a piecewise limiter. In virtual populations, there is inter-individual variability on individual kidney volume, GFRmat, TM50 (maturation), and the Hill coefficient for maturation (H). These values can be viewed for each individual by exporting a virtual population to .csv format. In non-preterm populations, the Post-menstrual age is equal to the Age in weeks + 40 weeks. The Hill coefficient for aging is fixed at 1.5. The aging half-times (TA50) are fixed at 54 and 59 years for males and females, respectively. The maximal decreasing factor is fixed at 0.9 mL/min/100g kidney. The volume of the standard kidney (Vstd) is 440 mL. These values are the same for all individuals in the population.
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Thank you for this @prvmalik! I'm noticing that the PK-Sim Simulation Structure export file from v9.1 defines Vstd as the standard kidney volume. If so, the intended units for GFRspec would not be achieved. Any idea if this is a typo in the export file? |
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In your screenshot V_kid_std (0.44L) is used as (0.44kg) to arrive at the units of (L/min/kg organ) by implying a density of 1 g/mL. You cannot change TM50 without: If I recall correctly GFR premat is derived from the paper by Rhodin et al. Take care, |
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Is have question about the inter-individual variability that is mentioned: How is this variability determined? Is it linked to a physiologic parameter? |
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@prvmalik |
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No. The GFR in mL/min in PKSim would be divided by the individual's BSA (Mosteller formula usually), and then multiplied by 1.73m2. |
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@prvmalik |
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Hello, may I ask how I found the creatinine clearance and how to fill this value into PKSIM? |
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Hi, I would like to know how to get from the GFRspec (ml/min/100g kidney) to the GFR of a simulated individual (ml/min). |
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Hi, PK-Sim assumes a density of 1 g/mL for all organs, meaning that 100 g of kidney tissue is equivalent to 100 mL in volume. I hope this information helps! Best, Tobias |
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Thank you! |
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Hi，May I ask how to caculate the kidney volume in the PK-sim? |
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The volume is not calculated but based on a physiology database. So, it was derived from biomedical knowledge, from which a database was generated. |
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Thanks a lot！ May I know where I can download such a database? |
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I am attaching the full equation for specific GFR in PK-Sim. Specific GFR (mL/min/100g kidney) is then multiplied out by the individual's kidney volume to get the individual GFR (mL/min). Be aware that the GFR would then need to be standardized by the individual BSA if comparing to clinical measurements, which are reported in units of mL/min/1.73m2.
The hill function for aging does not apply when age is less than 30. There is a piecewise limiter.
In virtual populations, there is inter-individual variability on individual kidney volume, GFRmat, TM50 (maturation), and the Hill coefficient for maturation (H). These values can be viewed for each individual by exporting a virtual population to…