SP264CLINICAL IMPACT OF INTER-LABORATORY VARIABILITY OF PARATHYROID HORMONE MEASUREMENT IN HEMODIALYSIS PATIENTS
Bibliographic record
Abstract
INTRODUCTION: There are many available PTH assays and inter-method variability between these assays is well documented. As a result, Chronic Kidney Diseases-Bone and Mineral Disorders (CKD-BMD) management guidelines now recommend using assay specific treatment thresholds. It is not known whether this actually reduces between center variability in the clinical management of CKD-BMD. The aim of this study is to elucidate whether inter-laboratory variability in PTH assays results in clinically significant differences in the management of CKD-MBD in hemodialysis (HD) patients. METHODS: Eighty-nine consecutive adult HD patients receiving care at Kingston General Hospital were asked to provide one additional blood sample at the time of routine bloodwork. Split samples from each patient were distributed to nine laboratories throughout Southern Ontario, Canada for PTH measurement. PTH all-methods mean (AMM), standard deviation (SD), coefficient of variation (CVa) and range were determined for each patient. Patients whose PTH range spanned the guideline thresholds of 2 – 9 times the assay-specific upper limit of normal (ULN) were identified and the percent of laboratories that would recommend a change in calcitriol prescription using a simplified clinical decision rule was calculated for each. RESULTS: Significant interlaboratory variability in PTH measurement continues to exist (one-way ANOVA, p < 0.0005). Individual patient PTH CVas ranged from 12.2% to 68.3%, with a mean CVa of 26.1%. On average, individual patient PTHs differed 2.3-fold from lowest to highest PTH value. Thirty-three (38%) patients had PTH range that spanned a clinically significant threshold (<2 and/or >9 x ULN). Treatment recommendations varied significantly between laboratories with some laboratories much more likely to result in low frequency of calcitriol prescriptions, and others a high frequency of calcitriol prescriptions. CONCLUSIONS: Significant interlaboratory variability in PTH measurement exists and results in center to center differences in CKD-MBD assessment despite the use of assay specific treatment cut-offs. The variability around the clinical thresholds is problematic and likely results in differences in management of CKD-BMD between centers. PTH assay standardization using reference standard materials is required to reduce the impact of assay type on patient management.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".