2. Improving the urine spot protein/creatinine ratio by the
estimated creatinine excretion to predict proteinuria in
pediatric kidney transplant recipients
Said Incir, Mehmet Tasdemir, Burak Kocak Berna Yelken,Emre Arpali, Basak Akyollu, Kerim Erhan
Palaoglu, Arzu Baygul, IlmayBilge,AydinTurkmen
Published in Paediatric Transplantation 2021
5. • It is known that detecting an increase in protein excretion has both diagnostic and prognostic value in the
initial confirmation of kidney disease.
• The assessment of proteinuria may have an essential value in evaluating the effectiveness of treatment
and disease recurrence or progression.
• Albuminuria and proteinuria, common in kidney transplant recipients, have been associated with
deteriorating kidney functions, increased risk for cardiovascular disease, graft loss, and mortality.
6. INTRODUCTION (CONTD…)
• For quantitative assessment of proteinuria, 24 h (24 h) urine collection remains the gold standard method.
• Collection is inconvenient and may lead to problems, volume or poor hygiene,particularly in young children.
• Day-to-day variability is another problem in assessing 24 h proteinuria as the change in the amount of
proteinuria over time may be associated with disease, therapy,or test variability.
• The Kidney Disease: Improving Global Outcomes(KDIGO) guidelines recommend using the spot (untimed)
albumin/creatinine (Spot A/Cr) or protein/creatinine (Spot P/Cr) ratio calculated from the first-morning void for
an alternative to the 24 h testing.
7. INTRODUCTION (CONTD…)
• In spot urine ratios, creatinine is used as a correction factor in the denominator, daily creatinine excretion rate
(CER) is accepted as 1 g/day.
• This assumption may not always be correct due to older age, female sex, lower body weight, or the impact of
chronic steroid exposure on muscle mass and turnover, especially in kidney transplant recipients.
• Having lower muscle mass leads to lower urine creatinine excretion and hence higher Spot P/Cr.
• Another limitation of the Spot P/Cr is that it does not consider the deviation for inter-individual variability in
daily creatinine excretion.
8. INTRODUCTION (CONTD…)
• Urinary CER varies noticeably due to anthropometric factors ,therefore the results of other studies from other
populations should not be employed on pediatric patients.
• There are several equations for calculating 24 h estimated creatinine excretion rate (eCER) in adults
(Goldwasser et al., Rule et al., Ix et al., or Fotheringham et al).
• Only a few equations are available for evaluating eCER in children.
9. INTRODUCTION (CONTD…)
• Spot P/Cr is a determination of protein excretion rate (PER) per unit of muscle mass
• Multiplying Spot P/Cr by eCER would hypothetically enhance the correlation and agreement
between Spot P/Cr and measured 24 h urine proteinuria (m24 h UP).
.
10. AIM OF THE STUDY
To determine the most applicable equation for predicting daily CER and examine whether
ePER values acquired from different equations can anticipate measured 24 h urine
protein (m24 hUP) better than Spot P/Cr in pediatric kidney transplant recipients.
12. STUDY POPULATION
• Medical records of 23 children with kidney transplantation were investigated retrospectively from November 2020 to
February2021.
• Exclusion criteria : age>than 18 years,
acute rejection,
any infectious condition,
decreased kidney function[(GFR) of<60ml/min/1.73 m2]
acute kidney injury, malignancies,
missing data, inappropriate urine collection.
• The present study protocol was reviewed and approved by the Institutional Review Board of Koç .
13. Urine sample collection
• Two urine collection cups, a container, and urine collection instructions were given to children and their parents. .
• Spot urine was obtained as the first-morning urine after finishing the second12 h urine collection.
• During the analysis, urinary protein and creatinine excretions were measured separately in the 12 h urines
• The two different containers combined in the same container and measured once more to measure the 24 h protein
excretion.
• The collection adequacy was validated by measuring urinary creatinine excretion ranges and was considered inappropriate
if daily creatinine excretion was <15 mg/kg/d in boys and12 mg/kg/d in girls.
14. MEASUREMENTS AND EQUATIONS
• Urine creatinine and protein were measured by Jaffe and turbidimetric method, respectively,
via Roche Cobas 6000 analyzer (Roche).
• 24 - hour protein excretion was adjusted for the patients’ body surface area according to the
DuBois formula.
15. MEASUREMENTS AND EQUATIONS(CONTD…)
• The formulas used in this study :
• Measured 24 h creatinine excretion rate
m24 h CER (g/d) = [Urine creatinine (mg/dL) × 24h Urine volume(ml)/100]/1000
• Measured 12 h creatinine excretion rate
m12 h CER (g/12h) = [Urine creatinine (mg/dL) × 12 h urine volume(ml)/100]/1000.
• Measured 24 h urinary protein excretion
m24 h UP (g/m2/d) = [Urine protein (mg/dl) × 24 h urine volume (ml)/100 /BSA]/1000.
18. STATISTICAL ANALYSIS
• Mean and standard deviation calculated for normally distributed continuous variables
• Median, minimum, maximum values were used to express non-normally distributed continuous variables.
• The qualitative variables were indicated as percentages.
• The normality of parameters was assessed by using the Shapiro-Wilk test.
• Kruskal-Wallis with Dunn’s multiple comparison test to detect a significant difference among first 12 h protein,
second 12 h protein, and 24 h protein values.
• Correlations of urine eCER and ePER were achieved after log transformation
• The Pearson correlation coefficient (r) was used to appraise the diagnostic concordance of the methods.
19. STATISTICAL ANALYSIS
• Passing-Bablok regression analysis was performed to evaluate the accuracy of the methods to predict 24 h urine
proteinuria.
• Both the intercept(α) and slope (β) between spot and 24 h urinary samples were assessed.
• Bland-Altman analysis for the bias estimation
• All statistical tests were two-tailed, and significance was considered as p <.05.
• Statistical analysis was performed using the MedCalc Statistical Software version 12.7.7
21. Demographics of
patients included in
study
• Data expressed as median (min-max) for non-normal
distribution, expressed as mean + SD for normally distribution and
reported as n (%);regardless of distribution
22. clinical and laboratory
findings of the patients
• Abbreviations: CER, Creatinine
excretion rate; PER, Protein excretion
rate; UP, Urine proteinuria.
23.
24. Correlation (I), Passing-Bablok(II) and the Bland-Altman(III) between measured 24 h urinary
protein (m24 h UP) and spot protein-to-creatinine ratio (Spot p/Cr)
25. Correlation (I), Passing-Bablok(II) and the Bland-Altman(III) between measured 24 h urinary protein (m24 h UP) and estimated
protein excretion rate (ePER) calculated by the Cockcroft-Gault
26. Correlation (I), Passing-Bablok(II) and the Bland-Altman(III) between measured 24 h urinary protein (m24 h UP) and estimated
protein excretion rate (ePER) calculated by Ghazali-Barratt
27. Correlation (I), Passing-Bablok(II) and the Bland-Altman(III) between measured 24 h urinary
protein (m24 h UP) and estimated protein excretion rate (ePER) calculated by Hellerstein
equations
28. Passing-Bablok and Bland-Altman analysis showing agreement among measured urine 24 h
protein and the spot protein-to-creatinine ratio (Spot P/Cr) or estimated protein excretion rate
(ePER) equations
30. • A strong correlation between m24 h CER and eCER values obtained by equations.
• The predictive capability of Spot P/Cr to assess proteinuria was improved, and bias was
decreased when adjusted by equations.
• All three formulas (Cockcroft-Gault,Ghazali-Barratt,and Hellerstein) displayed a strong
correlation in predicting m24 h CER and showed a better correlation and less bias than
the Spot P/Cr in evaluating 24 h proteinuria in pediatric kidney transplant recipients.
31. DISCUSSION (CONTD…)
• Determination of urinary protein excretion is a widely usedmethod in detecting, diagnosing, following, and
managing people at risk of developing kidney disease or recurrence, such as transplant patients,and is
considered a part of routine check-ups.
• Although collecting24 h urine is generally recommended for proteinuria evaluation, it is pretty laborious.
( In a children's study, Yang et al.8 discarded 30% of 24 h urine samples due to incomplete collection.)
32. DISCUSSION (CONTD…)
• In the clinical approach, proteinuria is usually calculated from spot urine rather than 24 h urine since
several studies have shown a high correlation between proteinuria in untimely spot samples an PER in 24
h urine samples
• Previous studies have shown that CER is approximately 15–25 mg/kg per day in men and 10–20mg/kg per
day in women.
• Given that the 24 h CER in healthy individuals is almost 1 g/day,using a simple ratio of spot urine protein
and creatinine concentrations may mirror m24 h UP.
• Age and body weight substantially affects body composition and mass in growing children.Hence, daily
CER should be calculated according to age and weight, especially in the pediatric population.
33. DISCUSSION (CONTD…)
• There was no study focused on pediatric kidney transplant recipients to examine the correlation.
• The highest correlation coefficient (r = 0.819) was observed among patients with transplantation with first
m12 h CER in predicting m24 h CER.
• eCER values calculated by Cockcroft-Gault,Ghazali-Barratt, and Hellerstein equations had a stronger
correlation with m24 h CER than the second m12 h CER
34. DISCUSSION (CONTD…)
• For accuracy and precision, the criteria the 95% CI of intercept and slope should include 0.0 and 1.0,
respectively.
• In this study, all the Spot P/Cr and three equations have met this criterion.
• Besides, the p-values obtained by the Passing-Bablok analysis were greater than 0.05, showing that no
significant deviation was observed from the linearity for all methods.
• The slope value closest to 1 was acquired on the regression line obtained with the Hellerstein equation.
35. DISCUSSION (CONTD…)
• To determine the concordance of Spot P/Cr and estimated versus m24 h UP for each formula, we analyzed the mean
bias and 95% limits of the agreement via the Bland-Altman plots.
• If there is no systematic error, the points are spread randomly on both sides of the straight line corresponding to the
difference 0 between measurements.
• The bias value obtained with all three equations was very close to each other and very low compared to the Spot
P/Cr.
• Results indicated that compared with Spot P/Cr, ePER values were closer to m24 h UP
• No study investigated the correlation and agreement between Spot P/Cr and 24 h UP in pediatric kidney transplant
recipients.
36. CONCLUSION
• The eCER obtained with the Cockcroft-Gault, Ghazali-Barratt, or Hellerstein formulas can be used to
calculate ePER and replace SpotP/Cr in routine screening for proteinuria in the pediatric kidney transplant
recipients.
• Utilizing these formulas may improve the accuracy and reduce the spot samples’ bias, and automated
eCER reporting can be applied to expand ePER in clinical practice.
37. LIMITATIONS
Study was performed at a single centre and the sample size was low
Formulas to estimate CER that have not been validated in pediatric kidney transplant recipients.
Preanalytical errors in urine collection, inspite of detailed instruction on how to collect the sample.
FUTURE ASPECT
Study need to be performed on larger sample size to confirm the results
39. Abstract, title and references
• Yes , the aim was of the study was clear to
as they wanted to improve precision of 24
hr proteinuria in routine clinical scenario
Is the aim clear?
• Yes,
Is it clear what the
study found and
how they did it?
• YesYes, the title well explained and what
they want to do in this study
Is the title
informative and
relevant?
40. Introduction
• Yes, the previous included in the study
explain what has been studied so far on ly in
adults
Is it clear what is
already known about
this topic?
• Yes, the research question is clearly outlined
Is the research
question clearly
outlined?
• Yes, but the topic has been studied in adults ,
it is the first attempt to develop such formula
for pediatric kidney transplant patients.
Is the research
question justified given
what is already known
about the topic?
41. Materials and methods
• Yes, medical records of 23 transplant patients were studied
retrospectively for the purpose
Is the process of subject
selection clear?
• Yes, they were measured appropriately
Are the variables defined and
measured appropriately?
• Yes, but since it’s a retrospective study consent was not required.
Are the study methods valid and
reliable?
• Yes, all the demographic has been explained of patients and
controls to replicate the studies.
Is there enough detail in order to
replicate the study?
42. Results
• Yes, the data was expressed appropriately
Is the data presented in an
appropriate way?
• Yes, the text helps in explaining the data shown in results and
repeatitive for some points
Does the text in the results add
to the data or is it repetitive?
• Yes, statistically significant was highlighted clearly and properly
explained
Are you clear about what is a
statistically significant result?
• Yes,
Are you clear about what is a
practically meaningful result?
43. Discussion and Conclusion
• Yes
Are the results discussed from
multiple angles and placed into
context without being
overinterpreted?
• Yes, the conclusion answers the study, but it needs to be
studied in larger population
Do the conclusions answer the
aims of the study?
• Yes, the results supports the conclusion .
Are the conclusions supported by
references or results?
44. Discussion and Conclusion
Are the limitations of the study fatal or are they opportunities to inform future research?
• No, limitations of the study are not fatal, and the authors have envisioned various possibilities for future
researches such as to do a comparison study between these instruments including cases of
hemoglobinopathies in the respective population
45. Overall
• Yes, the study design was appropriate to
answer the aim
Was the study design
appropriate to answer the
aim?
• The known equations are only applied in adult
population, but the study implies that it can be
used in pediatric patients as well
What did this study add
to what was already
known on this topic?
• No, there were no such major flaws
What were the major
flaws of this article?
• Yes, the article provides the required
information adequately.
Is the article consistent
within itself?
