-
Views
-
Cite
Cite
Etienne Cavalier, Pierre Delanaye, Laura Vranken, Anne-Catherine Bekaert, Agnès Carlisi, Jean-Paul Chapelle, Jean-Claude Souberbielle, Interpretation of serum PTH concentrations with different kits in dialysis patients according to the KDIGO guidelines: importance of the reference (normal) values, Nephrology Dialysis Transplantation, Volume 27, Issue 5, May 2012, Pages 1950–1956, https://doi.org/10.1093/ndt/gfr535
Close - Share Icon Share
Abstract
The recommended target range for serum parathyroid hormone (PTH) in dialysis patients has changed from 150 to 300 pg/mL in the KDOQI guidelines to two to nine times the upper normal limit in the KDIGO ones. Although inclusion/exclusion criteria for the reference population are highly important, they are usually not mentioned in the commercial kits. In this study, we used the same reference population of vitamin D-replete normal subjects to establish reference values for 10 commercial PTH kits. We evaluated whether this may improve the classification of dialysis patients according to the KDIGO compared to the use of reference values proposed by the manufacturers.
We measured serum PTH with 10 different kits in 149 haemodialysis patients, and 240 25-OH-vitamin D-replete (>75 nmol/L) individuals with an estimated glomerular filtration rate >60 mL/min/1.73 m 2 .
For the 10 kits, our upper normal limit was lower than those of the manufacturers. The difference was, however, variable from one kit to another. The two kits that yielded the lowest and the highest absolute concentrations classified differently 84/149 patients (56.4%) according to the KDOQI and 53/149 (36.2%) according to the KDIGO using the manufacturers’ normal values. Using our normal values significantly decreased the discrepancies with 24/149 patients (16.1%) being still classified differently. Taking the measurement uncertainty into consideration, 8% of the patients only remained differently classified by these two kits.
Using the same vitamin-D-replete population to establish the reference range for 10 commercial PTH kits significantly improved the classification of haemodialysis patients according to the KDIGO target range.
Comments
Dear Sir,
We read with interest the recent article by Cavalier et al. [1] regarding the effect of PTH assay reference range on achieving treatment targets in haemodialysis patients. We recently switched second-generation intact PTH (iPTH) assay from the Immunolite 2500 system (I2500) (Siemens, Los Angeles, CA, USA) to the Cobas Elecsys system (CE) (Roche Diagnostics, Indianapolis, IN, USA). During the transition, we assessed the inter-assay iPTH variability for these two assays to determine whether our iPTH target range for dialysis patients needed to be altered.
We tested 349 EDTA samples simultaneously with both I2500 assay (reference range = 16-87 pg/mL) and CE assay (reference range = 15-65 pg/mL). Although the assays were highly correlated (r2 = 0.96), there was a significant reduction in iPTH values recorded with the CE assay (median PTH 98.9 pg/mL vs. 134 pg/mL p<0.001). This difference was most marked at higher levels of the iPTH range. There was a mean reduction in iPTH (95% CI) by 31.2% (2%), 35.1% (3%) and 34.7% (3%) in patients who were in the iPTH ranges of 150-300 pg/mL, 300-450 pg/mL and > 450 pg/mL, respectively, by the outgoing I2500 assay. This corresponded to significantly lower median values with the CE assay (195 pg/mL vs. 133 pg/mL, 383.5 pg/mL vs. 241.8 pg/mL and 620 pg/mL vs. 431.4 pg/mL, respectively, P <_0.0001 for="for" all.="all." median="median" pth="pth" values="values" were="were" significantly="significantly" lower="lower" in="in" all="all" stages="stages" of="of" chronic="chronic" kidney="kidney" disease="disease" ckd="ckd" ckd3="ckd3" ckd4="ckd4" ckd5="ckd5" and="and" ckd5d-="ckd5d-" _74.3="_74.3" pg="pg" ml="ml" vs.="vs." _96="_96" _92.8="_92.8" _125="_125" _199.9="_199.9" _274.5="_274.5" _283.5="_283.5" _409.5="_409.5" respectively.="respectively." p0.001="p0.001" dialysis="dialysis" patients="patients" this="this" translated="translated" into="into" similar="similar" proportions="proportions" meeting="meeting" target="target" ipth="ipth" range="range" _56.5-="_56.5-" _54.3.="_54.3." however="however" _30="_30" previously="previously" rangen="50)" now="now" fell="fell" below="below" the="the" target.="target." second-generation="second-generation" assays="assays" can="can" distinguish="distinguish" high="high" or="or" low="low" bone="bone" turnover="turnover" with="with" some="some" accuracy="accuracy" _2.="_2." there="there" remains="remains" variance="variance" corresponding="corresponding" to="to" degree="degree" preventing="preventing" precise="precise" assessment="assessment" by="by" alone="alone" _3.="_3." certain="certain" fragments="fragments" demonstrating="demonstrating" antagonistic="antagonistic" effects="effects" pth4="pth4" it="it" is="is" possible="possible" that="that" treatment="treatment" based="based" on="on" may="may" lead="lead" over-suppression="over-suppression" turnover.="turnover." third-generation="third-generation" measuring="measuring" bioactive="bioactive" whole="whole" only="only" have="have" not="not" been="been" definitively="definitively" shown="shown" be="be" superior="superior" at="at" detecting="detecting" abnormal="abnormal" _25.="_25." thus="thus" short="short" performing="performing" biopsies="biopsies" get="get" more="more" reliable="reliable" non-invasive="non-invasive" data="data" than="than" unless="unless" further="further" bone-="bone-" specific="specific" biomarkers="biomarkers" are="are" validated.="validated." hence="arises" a="a" clinical="clinical" dilemma="dilemma" adjusting="adjusting" an="an" arbitrary="arbitrary" necessarily="necessarily" correlate="correlate" underlying="underlying" disease.="disease." given="given" reduction="reduction" _30-35="_30-35"> 150 pg/mL, we reduced the upper limit of the target iPTH range for CKD5d by a corresponding 30%, in order to continue current practice.
1. Etienne Cavalier, Pierre Delanaye, Laura Vranken, et al. Interpretation of serum PTH concentrations with different kits in dialysis patients according to the KDIGO guidelines: importance of the reference (normal) values. Nephrol. Dial. Transplant. 2012; 27, (5): 1950-1956.
2. Lehmann G, Stein G, H?ller M, et al. Specific measurement of PTH (1-84) in various forms of renal osteodystrophy (ROD) as assessed by bone histomorphometry. Kidney Int. 2005; 68, (3):1206-14.
3. Herberth J, Monier-Faugere MC, Mawad HW, et al. The five most commonly used intact parathyroid hormone assays are useful for screening but not for diagnosing bone turnover abnormalities in CKD-5 patients. Clin Nephrol. 2009; 72, (1):5-14.
4. Huan J, Olgaard K, Nielsen LB et al. Parathyroid hormone 7-84 induces hypocalcemia and inhibits the parathyroid hormone 1-84 secretory response to hypocalcemia in rats with intact parathyroid glands. J Am Soc Nephrol 2006; 17: 1923-1930.
5. Coen G, Bonucci E, Ballanti P, et al. PTH 1-84 and PTH "7-84" in the noninvasive diagnosis of renal bone disease. Am J Kidney Dis. 2002; 40, (2):348-54.
Conflict of Interest:
None declared