Modified Schwartz formula and 99mTc-DTPA plasma clearance methods to calculate glomerular filtration rate in critically ill children

Rohit Bhowmick; Ramachandran Rameshkumar; Madhusudhanan Ponnusamy; Vishnukumar Rajaraman; Muthu Chidambaram; Abraar Sheriff; Subramanian Mahadevan

doi:10.1007/s00467-021-05197-3

Modified Schwartz formula and ^99mTc-DTPA plasma clearance methods to calculate glomerular filtration rate in critically ill children

Pediatr Nephrol. 2022 Apr;37(4):899-906. doi: 10.1007/s00467-021-05197-3. Epub 2021 Sep 21.

Authors

Rohit Bhowmick¹, Ramachandran Rameshkumar², Madhusudhanan Ponnusamy³, Vishnukumar Rajaraman³, Muthu Chidambaram^{1

4}, Abraar Sheriff¹, Subramanian Mahadevan¹

Affiliations

¹ Division of Pediatric Critical Care, Department of Pediatrics, Jawaharlal Institute of Postgraduate Medical Education and Research (JIPMER), Puducherry, 605 006, India.
² Division of Pediatric Critical Care, Department of Pediatrics, Jawaharlal Institute of Postgraduate Medical Education and Research (JIPMER), Puducherry, 605 006, India. krramesh_iway@yahoo.co.in.
³ Department of Nuclear Medicine, Jawaharlal Institute of Postgraduate Medical Education and Research (JIPMER), Puducherry, 605 006, India.
⁴ Department of Pediatrics, Saveetha Medical College, Chennai, Tamil Nadu, 600004, India.

PMID: 34546418
DOI: 10.1007/s00467-021-05197-3

Abstract

Background: Studies comparing the modified Schwartz formula with measured GFR (m-GFR) are lacking in critically ill children.

Methods: This prospective cohort study enrolled children aged 1 month to 12 years, within 24 h of admission. m-GFR measured by technetium-99m-labeled diethylenetriaminepentaacetic acid (^99mTc-DTPA) and calculated by Russell's two-sample slope-intercept method. Serum creatinine was estimated by modified Jaffe method and estimated GFR (e-GFR) calculated by modified Schwartz formula. The primary outcome was to find agreement between the two methods. Bias, precision, and accuracy were calculated. Secondary outcomes were the incidence of AKI (by p-RIFLE criteria) and the difference between the two methods to diagnose AKI.

Results: A total of 208 pairs were analyzed. e-GFR showed good agreement with m-GFR with a mean bias of -4.37 ml/min/1.73 m² and precision (SD of bias) of 33.07, 95% limit of agreement -69.18 to 60.45, and intraclass correlation of 74% (95%CI 66-80%, P < 0.001). e-GFR underestimated m-GFR by 19.8% (95% CI 7.9-31.7%). Accuracy of e-GFR values within 10%, 20%, and 30% of m-GFR were 68.3%, 72.6%, and 78.8%, respectively. Incidence of AKI within 24 h was 60.1% by e-GFR and 54.3% by m-GFR (kappa 0.569, P < 0.001; sensitivity of 85.8%, 95%CI (78-91.7%).

Conclusions: The modified Schwartz formula shows good agreement with ^99mTc-labeled DTPA double plasma sample clearance method for calculating GFR in critically ill children aged 1 month to 12 years. The underestimation of GFR should be kept in mind while applying the formula at the bedside in PICU.

Trial registration: Protocol accessible at Clinical Trial Registry of India (CTRI) www.ctri.nic.in . (Trial Registered Prospectively and Registration No. CTRI/2017/10/010014) ([Registered on: 06/10/2017] Trial Registered Prospectively.) (Title "Measured glomerular filtration rate using Diethylenetriaminepentaacetic acid (DTPA) renal scan versus estimated glomerular filtration rate using modified Schwartz formula in critically ill children: A prospective observational, analytical study."). A higher resolution version of the Graphical abstract is available as Supplementary information.

Keywords: Acute kidney injury; Agreement; Children; Glomerular filtration rate; Mortality.

Publication types

Observational Study
Research Support, Non-U.S. Gov't

MeSH terms

Acute Kidney Injury* / diagnosis
Child
Creatinine
Critical Illness
Female
Glomerular Filtration Rate
Humans
Male
Pentetic Acid
Prospective Studies
Technetium Tc 99m Pentetate*

Substances

Pentetic Acid
Creatinine
Technetium Tc 99m Pentetate

Associated data

CTRI/CTRI/2017/10/010014