Artifactual prolongation of activated partial thromboplastin time with PEGylated compounds in silica-based assays

To cite this article: Kristoffersen AH, Bj anes TK, Jordal S, Leh S, Leh F, Svarstad E. Polyvinylpyrrolidone induced artefactual prolongation of activated partial thromboplastin times in intravenous drug users with renal failure. J Thromb Haemost 2016; 14: 936-9. EssentialsProlonged activated partial thromboplastin times (APTT) were found in drug users with renal failure. An oral methadone solution containing polyvinylpyrrolidone (PVP) had been injected intravenously. Spiking normal plasma with increasing concentrations of PVP resulted in artifically prolonged APTT. APTT prolongation may indicate PVP deposits as underlying cause in patients with renal failure.Summary. Unexpectedly prolonged activated partial thromboplastin times (APTTs) were noted in several patients with chronic renal insufficiency and a history of intravenous drug abuse. Deposits of polyvinylpyrrolidone (PVP), an excipient in one oral methadone solution used in opioid maintenance programs, were found in renal biopsies. One case is described in detail, and this is followed by a summary of findings in 11 other patients and the results of an in vitro experiment in which plasma was spiked with PVP at increasing concentrations. APTTs measured with STA PTT automate (Stago) were prolonged in all patients and in spiked samples, whereas supplemental coagulation parameters and APTTs measured with HemosIL SynthAsil or Actin FSL (Siemens) were within reference intervals. These results indicate that interference with APTTs by PVP is reagent-dependent.We suggest that a prolonged APTT should raise the suspicion of PVP deposit-associated kidney disease in patients with chronic renal failure and a history of intravenous drug abuse.

Section: Discussionsupporting

confidence: 54%

Polyvinylpyrrolidone induced artefactual prolongation of activated partial thromboplastin times in intravenous drug users with renal failure

Kristoffersen

Bjånes

Jordal

et al. 2016

“…In addition, recently published studies have shown that glycoPEGylation affects APTT assays by interfering with contact activators (e.g. silica); however, other etiologies are also likely . The chromogenic assays are considered to be more robust, but even these assays are prone to variability.…”

Section: Discussionmentioning

confidence: 99%

Qualification of a select one‐stage activated partial thromboplastin time‐based clotting assay and two chromogenic assays for the post‐administration monitoring of nonacog beta pegol

Tiefenbacher

Bohra

Amiral³

et al. 2017

Background Nonacog beta pegol (N9-GP) is an extended half-life, glycoPEGylated recombinant human factor IX that is under development for the prophylaxis and treatment of bleeding episodes in hemophilia B patients. Considerable reagent-dependent variability has been observed when one-stage clotting assays are used to measure the recovery of recombinant FIX products, including N9-GP. Objective To qualify select one-stage clotting and chromogenic FIX activity assays for measuring N9-GP recovery. Methods The accuracy and precision of the one-stage clotting assay (with the STA-Cephascreen activated partial thromboplastin [APTT] reagent) and the ROX Factor IX and BIOPHEN Factor IX chromogenic assays for measuring N9-GP recovery were assessed in N9-GP-spiked hemophilia B plasma samples in a systematic manner at three independent sites, with manufacturer-recommended protocols and/or site-specific assay setups, including different instruments. Results For each of the three FIX activity assays qualified on five different reagent-instrument systems, acceptable intra-assay and interassay accuracy and precision, dilution integrity, reagent robustness and freeze-thaw and short-term sample stabilities were demonstrated. The STA-Cephascreen assay showed a limited reportable range at one of the three qualification sites, and the BIOPHEN Factor IX assay showed suspect low-end sensitivity at one of the three qualification sites. An individual laboratory would account for these limitations by adjusting the assay's reportable range; thus, these findings are not considered to impact the respective assay qualifications. Conclusion The one-stage clotting assay with the STA-Cephascreen APTT reagent, the ROX Factor IX chromogenic assay and the BIOPHEN Factor IX chromogenic assay are considered to be qualified for the measurement of N9-GP in 3.2% (0.109 m) citrated human plasma.

“…Furthermore, most manufacturers do not provide validated protocols for their assays for the various available automated coagulation assay platforms. Therefore, APTT‐based factor assays are perceived as the incumbent assay format, regardless of its documented performance limitations . The cost of training is also perceived as an obstacle; particularly given the relatively large number of ‘off‐hours’ staff that may be required to perform factor assays.…”

Section: Discussionmentioning

confidence: 99%

A computer‐based model to assess costs associated with the use of factor VIII and factor IX one‐stage and chromogenic activity assays

Kitchen

Blakemore

Friedman

et al. 2016

A computer-based model to assess costs associated with the use of factor VIII and factor IX one-stage and chromogenic activity assays.J Thromb Haemost 2016; 14: 757-64. EssentialsChromogenic factor VIII and factor IX assays have not been widely adopted partly due to perceived cost. Chromogenic assays may be needed for monitoring therapy with some extended half-life concentrates. Efficient use of reagents makes the costs of chromogenic and one-stage factor IX assays similar. A similar approach for factor VIII delivers lower costs for chromogenic compared with one-stage assays.Summary. Background: Measurement of coagulation factor factor VIII (FVIII) and factor IX (FIX) activity can be associated with a high level of variability using onestage assays based on activated partial thromboplastin time (APTT). Chromogenic assays show less variability, but are less commonly used in clinical laboratories. In addition, one-stage assay accuracy using certain reagent and instrument combinations is compromised by some modified recombinant factor concentrates. Reluctance among some in the hematology laboratory community to adopt the use of chromogenic assays may be partly attributable to lack of familiarity and perceived higher associated costs. Objectives: To identify and characterize key cost parameters associated with one-stage APTT and chromogenic assays for FVIII and FIX activity using a computer-based cost analysis model. Methods: A cost model for FVIII and FIX chromogenic assays relative to APTT assays was generated using assumptions derived from interviews with hematologists and laboratory scientists, common clinical laboratory practise, manufacturer list prices and assay kit configurations. Results: Key factors that contribute to costs are factor-deficient plasma and kit reagents for one-stage and chromogenic assays, respectively. The stability of chromogenic assay kit reagents also limits the cost efficiency compared with APTT testing. Costs for chromogenic assays might be reduced by 50-75% using batch testing, aliquoting and freezing of kit reagents. Conclusions: Both batch testing and aliquoting of chromogenic kit reagents might improve cost efficiency for FVIII and FIX chromogenic assays, but would require validation. Laboratory validation and regulatory approval as well as education and training in the use of chromogenic assays might facilitate wider adoption by clinical laboratories.