The development and evaluation of dose-prediction tools for allopurinol therapy (Easy-Allo tools)

AIMS

Dose escalation at the initiation of allopurinol therapy can be protracted and resource intensive. Tools to predict the allopurinol doses required to achieve target serum urate concentrations would facilitate the implementation of more efficient dose-escalation strategies. The aim of this research was to develop and externally evaluate allopurinol dosing tools, one for use when the pre-urate-lowering therapy serum urate is known (Easy-Allo1) and one for when it is not known (Easy-Allo2).

METHODS

A revised population pharmacokinetic-pharmacodynamic model was developed using data from 653 people with gout. Maintenance doses to achieve the serum urate target of <0.36 mmol L-1 in >80% of individuals were simulated and evaluated against external data. The predicted and observed allopurinol doses were compared using the mean prediction error (MPE) and root mean square error (RMSE). The proportion of Easy-Allo predicted doses within 100 mg of the observed was quantified.

RESULTS

Allopurinol doses were predicted by total body weight, baseline urate, ethnicity and creatinine clearance. Easy-Allo1 produced unbiased and suitably precise dose predictions (MPE 2 mg day-1 95% confidence interval [CI] -13-17, RMSE 91%, 90% within 100 mg of the observed dose). Easy-Allo2 was positively biased by about 70 mg day-1 and slightly less precise (MPE 70 mg day-1 95% CI 52-88, RMSE 131%, 71% within 100 mg of the observed dose).

CONCLUSIONS

The Easy-Allo tools provide a guide to the allopurinol maintenance dose requirement to achieve the serum urate target of <0.36 mmol L-1 and will aid in the development of novel dose-escalation strategies for allopurinol therapy.

Detection of Neuroinflammation Induced by Typhoid Vaccine Using Quantitative Magnetization Transfer MR: A Randomized Crossover Study

BACKGROUND

The role of neuroinflammation in psychiatric disorders is not well-elucidated. A noninvasive technique sensitive to low-level neuroinflammation may improve understanding of the pathophysiology of these conditions.

PURPOSE

To test the ability of quantitative magnetization transfer (QMT) MR at 3 T for detection of low-level neuroinflammation induced by typhoid vaccine within a clinically reasonable scan time.

STUDY TYPE

Randomized, crossover, placebo-controlled.

SUBJECTS

Twenty healthy volunteers (10 males; median age 34 years).

FIELD STRENGTH/SEQUENCE

Magnetization prepared rapid gradient-echo and MT-weighted 3D fast low-angle shot sequences at 3 T.

ASSESSMENT

Participants were randomized to either vaccine or placebo first with imaging, then after a washout period received the converse with a second set of imaging. MT imaging, scan time, and blood-based inflammatory marker concentrations were assessed pre- and post-vaccine and placebo. Mood was assessed hourly using the Profile of Mood States questionnaire. QMT parameter maps, including the exchange rate from bound to free pool (kba) were generated using a two-pool model and then segmented into tissue type.

STATISTICAL TESTS

Voxel-wise permutation-based analysis examined inflammatory-related alterations of QMT parameters. The threshold-free cluster enhancement method with family-wise error was used to correct voxel-wise results for multiple comparisons. Region of interest averages were fed into mixed models and Bonferroni corrected. Spearman correlations assessed the relationship between mood scores and QMT parameters. Results were considered significant if corrected P < 0.05.

RESULTS

Scan time for the MT-weighted acquisition was approximately 11 minutes. Blood-based analysis showed higher IL-6 concentrations post-vaccine compared to post-placebo. Voxel-wise analysis found three clusters indicating an inflammatory-mediated increase in kba in cerebellar white matter. Cerebellar kba for white matter was negatively associated with vigor post-vaccine but not post-placebo.

DATA CONCLUSION

This study suggested that QMT at 3 T may show some sensitivity to low-level neuroinflammation. Further studies are needed to assess the viability of QMT for use in inflammatory-based disorders.

EVIDENCE LEVEL

1 TECHNICAL EFFICACY: Stage 2.

'She taught me': factors consumers find important in nurse practitioner and pharmacist prescriber services

BACKGROUND

Advanced practitioner services, such as those nurse practitioners and pharmacist prescribers provide, are an opportunity to improve health care delivery. In New Zealand, these practitioners remain underutilised, despite research suggesting they offer safe and effective care, and considerable international literature recording patient satisfaction with these roles. This study aimed to explore factors underlying consumer satisfaction with primary health care nurse practitioner and pharmacist prescriber services.

METHODS

As part of a larger realist evaluation, 21 individuals receiving advanced practitioner services participated in semi-structured interviews. These interviews were transcribed and coded against context-mechanism-outcome configurations tested and refined throughout the research.

RESULTS

Study findings emphasise the importance of consumer confidence in the provider as a mechanism for establishing advanced practitioner roles. Underlying this confidence is a recognition that these practitioners work in a more accessible manner, engage at the individual's 'level', and operate with passion.

CONCLUSIONS

This research offers learnings to re-engineer service delivery within primary health care to make best use of the entire health care team by including consumers in the design and introduction of new roles.