Agreement between one stage and chromogenic assays in samples from patients receiving recombinant porcine FVIII (Obizur, Susoctocog-alfa)

INTRODUCTION

Recombinant porcine FVIII (rpFVIII) (Obizur, Susoctcog-alfa, Takeda, Japan) is licensed for the treatment of bleeding in acquired Haemophilia A (AHA). The summary of product characteristics state that monitoring should be by one stage assay (OSA) rather than chromogenic assay (CSA). CSA have been shown to underestimate activity when rpFVIII is added to plasma in vitro.

METHODS

Samples from three AHA patients (n = 21) (pre- and post rpFVIII) were assessed using FVIII:C assays; OSA methods: Actin, Actin FS, Actin FSL and Pathromtin SL performed on CS5100i (Sysmex, Kobe, Japan); APTT-SP, SynthASil and SynthAFax performed on ACL TOP (Werfen, Barcelona, Spain). CSA methods on CS5100i: Siemens Chromogenic Assay, Biophen FVIII:C, Technochrom FVIII:C; on ACL TOP: Rox Factor VIII, Coamatic Factor VIII and CRYOcheck Factor VIII.

RESULTS

OSA and CSA varied according to reagent used median OSA 61 IU/dL (range 41.5-81 IU/dL (ANOVA p < 0.0001)) median CSA 46.5 IU/dL (range of method specific medians 36.5-84 IU/dL (ANOVA p < 0.0001)). Amongst OSA, Actin FS was associated with the highest FVIII:C, APTT-SP was associated with the lowest. Variation in CSA results by different methods was also seen with highest FVIII:C levels obtained using the Technochrom FVIII:C and the lowest levels obtained with Siemens Assay.

CONCLUSION

The relationship between OSA and CSA was not consistent between method or patient. Previously there has been reports of underestimation by CSA in in vitro spiked samples. Investigation into concentration of phospholipids in the APTT reagents may explain some of these variations.

How to assess parallelism in factor assays: coefficient of variation of results with different dilutions or slope ratio?

INTRODUCTION

Non-parallelism in factor assays can lead to incorrect factor activities. Parallelism can be assessed by calculating the coefficient of variation (CV) of results obtained on 3 dilutions of the same sample. Some authors have proposed that if there is <15% then the average activity is reportable. Some analysers use a slope ratio (SR) to calculate parallelism, with an acceptance range of approximately 0.9-1.1.

METHODS

We evaluated CV and SR in one stage FII-FXII assays on Sysmex CS5100i using Innovin or Actin FS. Frozen normal and pathological plasmas, plasmas containing Direct Oral Anticoagulants, Direct Thrombin Inhibitors or Lupus Anticoagulant were analysed to assess possible non-parallelism.

RESULTS

In plasmas with factor levels >25 IU/dl (plus no interfering substances) all CVs were < 15%. One sample (low factor activities 10-15 IU/dl), had CVs > 15% in FII, FVII and FXII assays only. SR outside of 0.9-1.1 were seen in FII and FXII assays at different levels of clotting factor including some within the normal range. Non-parallelism was detected more frequently with SR than CV for those with interfering substances.

CONCLUSIONS

SR outside of 0.9-1.1 were seen in different levels of clotting factors, including samples which did not contain interfering substances. The target of 15% CV was a better discriminator than a SR for acceptance. When factor levels were reduced to around 10-15 IU/dl, a target 20 %CV was more appropriate than 15%. It might be appropriate for laboratories to assess locally whether their acceptance criteria need to be wider at low levels of clotting factors.

Improving pain management after total joint replacement surgery

PURPOSE

To test the effects of implementing evidence-based postoperative pain management content and strategies on patient, provider (nurse and physician), and fiscal outcomes.

SAMPLE

118 patients, 57 before and 61 after implementation, having total knee replacement (TKR) (54%) and total hip replacement (THR) (45%), and 28 orthopaedic nurses.

METHODS

A research utilization approach with a pretest/posttest design was used. Independent variables (interventions) included evidence-based pain management content, education of care providers and patients, and system changes at the point of care. Dependent variables (outcomes) were patient perception of the postoperative pain experience, provider practice patterns, and length of stay (LOS).

FINDINGS

The hypotheses of decreased provider use of meperidine and increased use of hydromorphone, i.v. route, pain plans of care, and nurse knowledge were supported. LOS was significantly reduced. The patient hypotheses decreased pain intensity and side effects and increased satisfaction and function were not supported.

CONCLUSION

Methodical implementation of evidence-based pain management information changed practice and fiscal outcomes. Improvement in the patient perception of pain management was more difficult to achieve.

Diarrhea associated with lorazepam solution in a tube-fed patient

A 43-year-old patient with adult respiratory distress syndrome, alcoholic hallucinosis, and delirium required significant amounts of lorazepam, morphine, and midazolam for management of agitation and increased peak airway pressures. Broad-spectrum antibiotics and intermittent pancuronium therapy were instituted. A nasoenteral feeding tube was placed for nutrition and medication administration during mechanical ventilation. Tube feedings were well tolerated except for intermittent bouts of large amounts of diarrhea. Clostridium difficile culture and toxin results were negative. Lorazepam and morphine administration were converted from the IV to enteral route to decrease the amount of fluid administered. The tube feeding was changed to an electrolyte rehydration solution and eventually discontinued. A search for drug-related contributing factors to the diarrhea revealed polyethylene glycol present in the lorazepam solution. It was postulated that this could be a contributing cause to the diarrhea. The lorazepam solution was changed to enterally administered crushed tablets with subsequent resolution of diarrhea.

Postmortem changes and pharmacokinetics: review of the literature and case report

OBJECTIVE

To review the mechanisms and sequence of events that occur during ischemia and cell death and following death of the human body. The impact of these postmortem events on the distribution and pharmacokinetic behavior of drugs is described. The case study presented illustrates a possible situation where such postmortem changes could have affected the pharmacokinetics of procainamide.

DATA SOURCES

English-language journal articles and reference texts identified from pertinent data sources.

DATA SYNTHESIS

Postmortem changes in the human body begin at the cellular level with the onset of ischemia. As the length of time of ischemia increases and death ensues, more changes occur and lead to deterioration in tissue and organ function. These changes may affect the pharmacokinetic and distribution behavior of certain drugs. Drugs particularly affected are those whose distribution is dependent on molecular size, lipophilicity, pH, energy-dependent transport, and tissue binding. Such drugs include the tricyclic antidepressants, digoxin, and cimetidine. Other drugs with similar characteristics, such as procainamide, may also demonstrate like changes in distribution and pharmacokinetics.

CONCLUSIONS

When measuring drug concentrations after death, it is important to consider the phenomenon of postmortem redistribution. Postmortem drug concentrations may not be a true reflection of antemortem concentrations and as a result, wrong conclusions could be made about the cause of death. More studies characterizing the postmortem distribution and pharmacokinetic characteristics of specific drugs are necessary.