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Evidence for shrunken pore syndrome in children
Emil den Bakker1, Reinoud Jbj Gemke1, Joanna Ae van Wijk1
1Department of Pediatrics, Amsterdam University Medical Center, Amsterdam, the Netherlands.
Insights
Shrunken Pore Syndrome (SPS) in children is linked to smaller glomerular pores, affecting cystatin C and beta-trace protein levels. This study found SPS prevalence in children comparable to adults, suggesting potential implications for kidney function assessment.
Area of Science:
- Pediatric Nephrology
- Renal Physiology
- Biomarker Research
Background:
- The Shrunken Pore Syndrome (SPS) hypothesis links cystatin C and mortality to reduced glomerular filtration rate (GFR) due to smaller kidney pores.
- In adults, SPS suggests impaired filtration of larger molecules like cystatin C and beta-trace protein (BTP) while creatinine passes freely.
- This study aimed to investigate the applicability and characteristics of SPS in a pediatric population.
Purpose of the Study:
- To determine the prevalence and definition of Shrunken Pore Syndrome (SPS) in children.
- To compare kidney function markers and glomerular filtration rate (GFR) estimation in children with and without SPS.
- To explore the relationship between cystatin C, beta-trace protein (BTP), and creatinine in pediatric kidney function.
Main Methods:
- Studied 294 children undergoing inulin clearance (Cin) tests, measuring serum creatinine, cystatin C, and BTP.
- Calculated estimated GFR (eGFR) for all markers using full age spectrum equations.
- Analyzed ratios of eGFR markers (eGFRcys/eGFRcrea, eGFRcys/Cin) and correlated them with eGFR BTP error to define and assess SPS prevalence.
Main Results:
- The ratio eGFRcys/eGFRcrea positively correlated with eGFR BTP error (%), indicating impaired filtration.
- Prevalence of SPS in children was 4.8% using a specific eGFRcys/eGFRcrea cut-off.
- Children with SPS exhibited more negative eGFR errors and higher actual GFR (Cin), with creatinine eGFR overestimation noted under certain definitions.
Conclusions:
- The prevalence of Shrunken Pore Syndrome in children is comparable to that observed in adults.
- Cystatin C and BTP levels are related, independent of creatinine, supporting the glomerular pore size hypothesis in children.
- Further research defining SPS using exogenous clearance studies may clarify its impact on creatinine metabolism in pediatric populations.
Abstract:
The link between cystatin C and mortality independent of glomerular filtration rate (GFR) in adults has prompted the "Shrunken Pore Syndrome" (SPS) hypothesis, where high serum cystatin C with normal creatinine is explained by smaller glomerular pores, through which creatinine can pass freely, while the larger cystatin C, beta-trace protein (BTP) and pro-inflammatory molecules are retained. This study set out to apply the definition of SPS to children. In 294 children who underwent inulin clearance (Cin) test, serum creatinine, cystatin C and BTP were measured. For all three markers eGFRx was calculated using the full age spectrum equations. The ratio eGFRcys/eGFRcrea was plotted against the error of eGFRBTP(%) (i.e. eGFRBTP-Cin)/Cin*100%). Patients with and without SPS according to different cut-off points of eGFRcys/eGFRcrea and eGFRcys/Cin (i.e. ≤0.6,0.7,0.8) were compared in terms of eGFRx, Cin, error of eGFRx(%) and eGFRBTP/eGFRcrea-ratio. The ratio eGFRcys/eGFRcrea and error of eGFRBTP(%) were positively correlated. The prevalence of SPS by eGFRcys/eGFRcrea with a cut-off of 0.6 was 4.8%. Patients with SPS had a more negative error of eGFRcys(%) and eGFRBTP(%) and higher Cin regardless of the definition. Overestimation of eGFRcrea in patients with SPS was only present when using the eGFRcys/eGFRcrea rather than the eGFRcys/Cin definition. Cystatin C and BTP are related independent of creatinine, suggesting glomerular pore size as a common denominator. The prevalence of SPS in children is comparable to adults. For research in SPS, a definition based on eGFRcys/exogenous clearance study may be useful to study the effect of SPS on creatinine metabolism.
