Combining GFR estimates from cystatin C and creatinine-what is the optimal mix?

BACKGROUND

Combining estimated glomerular filtration rate (eGFR) equations based on creatinine and cystatin C has been shown to improve the accuracy of GFR estimation. This study aims to optimize this strategy for height-independent GFR estimation in children.

METHODS

Retrospective study of 408 inulin clearance tests with simultaneous International Federation of Clinical Chemistry-calibrated measurements of creatinine, cystatin C, and urea in children (mean age 12.5 years, GFR 91.2 ml/min/1.73m²) comparing the arithmetic (mean_arith) and geometric means (mean_geom) of a height-independent creatinine-based (full age spectrum, based on age (FASage)) and a cystatin C-based equation (FAScys), with the complex height-dependent CKiD3 equation incorporating gender, height, cystatin C, creatinine, and urea.

RESULTS

Mean_geom had a P₃₀ accuracy of 89.2% compared to mean_arith 87.7% (p = 0.030) as well as lower bias and %precision error and performed almost as well as CKiD3 (P₃₀ accuracy 90.9%). Modifying the weight of FASage and FAScys when calculating the means showed that an equal contribution was most accurate in most patients. In spina bifida patients, FAScys alone outperformed any combination. Malignancy or nephritis patients had slightly higher accuracy with weighted means favoring cystatin C or creatinine, respectively. Disagreement between FAScys and FASage was inversely correlated with the accuracy of mean_geom. When disagreement exceeded 40%, application of weighted means based on diagnosis improved the performance of eGFR.

CONCLUSIONS

In the absence of height data, the optimal strategy for estimating GFR in children is by using the geometric mean of FASage and FAScys. When there is large disagreement between the two, weighted means based on diagnosis improve accuracy.

Accurate eGFR reporting for children without anthropometric data

INTRODUCTION

Reporting estimated glomerular filtration rate (eGFR) instead of serum concentrations is advised in current guidelines. Most creatinine-based eGFR equations for children require height, a parameter not readily available to laboratories. Combining height-dependent creatinine- and cystatin C-based eGFR improves performance. Recently, a height-independent creatinine-based eGFR equation has been developed.

AIM

To compare the combination of height-independent creatinine- and cystatin C-based equations with a combination of equations using anthropometric data.

METHODS

Retrospective analysis of 408 pediatric inulin clearance studies with simultaneous height, creatinine, cystatin C and urea measurements. eGFR calculation using the recalibrated Schwartz_crea (height-dependent), FASage (height-independent) and the Schwartz_cys equation. The means (Schwartz_crea+Schwartz_cys)/2 and (FASage+Schwartz_cys)/2 were compared with the CKiD3 equation incorporating cystatin C, creatinine, urea, height and gender in terms of %prediction error and accuracy.

RESULTS

All three single parameter equations performed similarly (P₃₀ accuracy around 80%). (FASage+Schwartz_cys)/2 (P₃₀ 89.2%) and (Schwartz_crea+Schwartz_cys)/2 (P₃₀ 89.0%), performed comparably to CKiD3 (P₃₀ 90.0%). If the difference between the creatinine- and the cystatine C based eGFR was <40%, P₃₀ accuracy of the mean exceeded 90%.

CONCLUSION

Combining the height-independent FASage and Schwartz_Cys equations substantially improves accuracy and performs comparably to height-dependent equations. This allows laboratories to directly report eGFR in children.

Estimation of GFR in children using rescaled beta-trace protein

INTRODUCTION

Beta-trace protein (BTP) is a low molecular weight protein, produced mainly in the cerebrospinal fluid. It has been proposed as a marker for kidney function. Recently, a new method for GFR estimation using mean normal values to rescale GFR marker concentrations has been described for creatinine and cystatin C, two commonly used endogenous markers for kidney function. The aim of this study is to apply this approach to BTP in children.

METHOD

We retrospectively analyzed serum concentrations of creatinine, cystatin C and BTP measured during inulin clearance tests in children. BTP was measured using a particle-enhanced immunonephelometric assay (Siemens Healthcare). A novel BTP-based eGFR equation was developed using published normal values for children: eGFR_BTP[ml/min/1.73m²] = 107.3/BTP/Q_BTP with Q_BTP = 0.69. Performance of this equation was compared to the established creatinine-based full age spectrum equation FASage and the cystatin C-based FAScys equations as well as the BTP-based Benlamri equation in terms of bias, % prediction error and P₃₀ and P₁₀ accuracy rates.

RESULTS

322 inulin clearance tests were studied. Overall, our novel equation performed comparably to the creatinine-based FASage and the BTP-based Benlamri equations but was less accurate than FAScys (P₃₀: 79.2 vs 86.3%, p = .008). Combining markers significantly enhanced performance compared to the single marker equations, with the exception of FAScys.

CONCLUSION

Rescaled BTP concentrations are a simple method for estimating GFR in children. However, the additional value of BTP for the estimation of GFR compared to rescaled creatinine and cystatin C still remains to be demonstrated.

Perianal Abscesses in Infants Are Not Associated With Crohn's Disease in a Surgical Cohort

AIMS

The aim of this study is to search for an association between infantile perianal abscesses and [development of] Crohn's disease in a surgical population of children.

METHODS

Patients who were surgically treated in the Amsterdam UMC between January 2000 and December 2014 were included in this retrospective cohort study. Data collected include: sex, date of birth, underlying conditions, age of onset, additional symptoms, pus cultures, endoscopic examination, histological examination, magnetic resonance imaging, faecal calprotectin levels, antibiotic treatment, surgical treatment strategy, and number of recurrences. Follow-up data were gathered from medical records and by contacting the patients and/or parents or the general practitioner.

RESULTS

The study consisted of 62 patients of whom 60 were boys. Median age was 5 months [range 0-17 months]; 92% were under 1 year of age at diagnosis. A minority of patients had accompanying symptoms. In total, 72 abscesses were treated, 19 fistulas and 23 abscesses with fistula-in-ano. Follow-up data of 46 patients [74%] were available; none of the patients developed Crohn's disease.

CONCLUSIONS

We found no association between isolated perianal abscesses as presenting symptom in early childhood and [development of] Crohn's disease. In young infants with isolated perianal disease, risk for inflammatory bowel disease seems low. In this specific population there seems no place for routine performance of endoscopic investigations. One should always take the risk of very-early-onset inflammatory bowel disease into account. Further research with a larger cohort of children and a longer follow-up time is required.

Health-related quality of life and its determinants during and after treatment for paediatric acute lymphoblastic leukaemia: a national, prospective, longitudinal study in the Netherlands

OBJECTIVES

Health-related quality of life (HRQoL) is impaired in paediatric patients with acute lymphoblastic leukaemia (ALL). Over the past decades, ALL treatment has successfully been adjusted to the risk of relapse, which is now reflected by the stratification of patients into three risk groups who receive treatment of differing intensities. This study is the first to evaluate the longitudinal course of HRQoL in light of these adjustments and identify determinants of HRQoL.

DESIGN

Two prospective, national cohort studies (add-on studies within the two most recent treatment protocols for children with ALL (ALL-10 and ALL-11)).

SETTING

Dutch paediatric oncology hospitals between October 2006 and October 2009 (ALL-10) and between August 2013 and July 2017 (ALL-11).

PARTICIPANTS

Patients with ALL (2-18 years) are treated according to the ALL-10 or ALL-11 treatment protocol. Patients treated according to the ALL-10 protocol only completed a cancer-specific QoL measure and patients treated according to the ALL-11 protocol completed both a cancer-specific and generic QoL measure (see below).

OUTCOME MEASURES

HRQoL, assessed with parent-proxy questionnaires (PedsQL Generic and Cancer module) within the first 5 months (T0), at 1 year (T1), 2 years (T2) and 3 years (T3) after diagnosis. The proportion of patients with clinically relevant generic HRQoL impairment was compared with healthy norm values. Multivariable mixed model analyses were used to evaluate the development of HRQoL over time and its medical and sociodemographic determinants (collected on enrolment).

RESULTS

Of the ALL-10 cohort, 132 families participated and of the ALL-11 cohort, 136 families participated (268 total). Thus, cancer-specific HRQoL assessments were available for 268 patients (median age 5.3 years (IQR 6.15), 56.0% boys, 69.0% medium-risk ALL), and generic HRQoL assessments for 136 patients (median age 4.8 years (IQR 6.13), 60.3% boys, 75.0% medium-risk ALL). Generic HRQoL improved between timepoints T0 and T3 (total score B 16.1, 95% CI 12.2 to 20.1, p<0.001), but did not restore to normal 1 year after the end of treatment: 28.0% of children remained impaired compared with 16% in the general population (p=0.003). Cancer-specific HRQoL generally improved from T0 to T2 (Pain B 11.3, 95% CI 7.1 to 15.5; Nausea B 11.7, 8.4 to 15.1; Procedural Anxiety B 19.1, 14.8 to 23.4; Treatment Anxiety B 12.8, 9.5 to 16.0; Worry B 3.5, 0.6 to 6.3; Communication B 8.5, 5.0 to 11.9; all p<0.001 except for Worry (p=0.02)), while Physical Appearance and Cognitive Functioning remained stable. Higher treatment intensity and experiencing pain or simultaneous chronic illness were associated with lower HRQoL over time for multiple subscales.

CONCLUSIONS

HRQoL impairment is prevalent during and after ALL treatment. Patients with standard-risk ALL and reduced treatment intensity have better HRQoL than patients in higher risk groups. Systematic monitoring of HRQoL is of utmost importance in order to provide timely psychosocial interventions and supportive care.