Cross-Validation of the Foundation Pain Index with PROMIS-29 in Chronic Pain Patients

Purpose

Discovery and validation of pragmatic biomarkers represent significant advancements in the field of pain management. Evaluating relationships between objective biomarkers and patient-reported outcomes (PROs) is an effective way to gain mechanistic insight into the potential role of biochemistry in chronic pain. The aim of this study was to validate the Foundation Pain Index (FPI) by evaluating associations between deranged biochemical function and PROMIS-29 domains in individuals living with chronic pain.

Patients and Methods

PROMIS-29 scores and FPI test results were obtained from 298 patients with chronic pain in this retrospective, observational study. Statistical analysis was performed using clinical test data to evaluate relationships between deranged biochemical function and quality of life measures across 8 universal domains.

Results

FPI scores significantly associated with multiple PROMIS-29 domains including physical function, impact score, fatigue, pain interference, and depression (P < 0.05). Moreover, specific analytes that comprise the FPI significantly correlated with PROMIS-29 domains, including 5-hydroxyindolacetic acid (pain interference, physical function, and pain impact scores), hydroxymethylglutarate (physical function), homocysteine (pain impact scores), kynurenic acid (pain interference and physical function), and quinolinic acid (physical function) (P < 0.05).

Conclusion

Cross-validation of the FPI with PROMIS-29 domains further supports the role of deranged biochemical function in the etiology of chronic pain. Objective identification of atypical biochemical function and subsequent correction holds tremendous promise for the non-opioid management of pain. Continued research efforts will aim to determine the impact of biochemical optimization in pre-surgical periods and post-surgical outcomes in patients with chronic pain.

Association of urinary concentrations of phthalate metabolites with quinolinic acid among women: A potential link to neurological disorders

BACKGROUND

Quinolinic acid (QA), a neuroactive metabolite produced during tryptophan degradation, is implicated in the pathogenesis of several neurological disorders. Phthalates are structurally similar to QA, and exposure to phthalates has demonstrated increased QA production and excretion in rodent studies. We recently showed that very high exposure to dibutyl phthalate was associated with higher concentrations of urinary QA in men. However, no human studies examined the associations between background (low) phthalate exposures and QA.

OBJECTIVES

To examine the associations of urinary concentrations of phthalate metabolites with QA.

METHODS

Female participants (N = 126) who participated in a prospective cohort study at the Massachusetts General Hospital Fertility Center provided 758 urine samples (273 during pregnancy and 485 during non-pregnancy). Concentrations of 11 phthalate metabolites and QA in urine were measured. We used multivariable linear mixed effect models to estimate the percent change in urinary QA concentrations associated with a doubling (100%) of urinary phthalate metabolite concentration, and evaluated whether there was effect modification by pregnancy status.

RESULTS

Women's mean (standard deviation) age was 34.2 (4.0) years with a body mass index of 23.5 (3.7) kg/m2. The women were primarily Caucasian (92%), had at least a college degree (98%), and none were current smokers. Pairwise Spearman correlations between concentrations for phthalate metabolites and QA measured in the same urine samples ranged from 0.36 for MEHP to 0.68 for dibutyl phthalate (DBP) metabolites. In multivariable-adjusted models, the percent change in urinary QA concentrations was significantly higher for each doubling of several urinary phthalate metabolite concentrations. For example, each doubling of DBP metabolites was associated with a 13.7% (95%CI: 10.6, 16.9)% higher QA. Associations between the low molecular weight phthalate metabolites and QA were stronger among samples collected during pregnancy as compared to non-pregnancy samples from the same women.

CONCLUSIONS

Urinary concentrations of several phthalate metabolites were positively associated with QA among women. These findings, along with the known neurotoxicity of QA, warrant the need to examine whether QA concentrations may serve as a pathway for the adverse neurodevelopment outcomes found in children's health studies.

High phthalate exposure increased urinary concentrations of quinolinic acid, implicated in the pathogenesis of neurological disorders: Is this a potential missing link?

BACKGROUND

Quinolinic acid (QA), a neuroactive metabolite of the Kynurenine Pathway (KP), is an excitotoxin that is implicated in the pathogenesis of many neurological disorders. KP is the main tryptophan degradation pathway. Phthalates can structurally mimic tryptophan metabolites and diets containing phthalates in rats enhanced the production and excretion of QA. However, there are no human studies that have examined the association between phthalates and QA.

OBJECTIVES

Taking advantage of different mesalamine formulations with/without dibutyl phthalate (DBP), we assessed whether DBP from mesalamine (>1000x background) altered the urinary concentrations of QA.

METHODS

Men with inflammatory bowel disease participated in a prospective crossover pilot study. 15 Men were on non-DBP mesalamine (background) at baseline crossed-over for 4 months to high-DBP mesalamine (high) (B1H-Arm) and vice versa for 15 men who were on high-DBP mesalamine at baseline (H1B-Arm). Men provided 60 urine samples (2/man). We estimated crossover and cross-sectional changes in the creatinine normalized-QA using multivariable linear mixed effect models with random intercepts.

RESULTS

At baseline, men who were on high-DBP mesalamine (H1B-Arm) had 72%, (95% confidence interval (CI): 18, 151) higher normalized-QA than men who were on background exposure and when high-DBP mesalamine was removed for four months, normalized-QA decreased with 32%, (95% CI: -45.0, -15.1). Consistently, when men in B1H-Arm were newly-exposed to high-DBP mesalamine, normalized-QA increased with 11%, (95% CI: -11, 38).

CONCLUSIONS

High-DBP exposure from mesalamine increased the urinary concentrations of QA, which was largely reversed after removal of the high-DBP exposure for four months. This novel hypothesis should warrant new promising research considering the KP and QA concentrations as a plausible mediator for the neurotoxicity possibly linked with phthalate exposures.

The Determination of Morphine in the Larvae of Calliphora stygia using Flow Injection Analysis and HPLC with Chemiluminescence Detection

Selective determination of morphine in the larvae of Calliphora stygia (Fabricius) (Diptera: Calliphoridae) using acidic potassium permanganate chemiluminescence detection coupled with flow injection analysis and high-performance liquid chromatography (HPLC) is described. Larvae of C. stygia were reared on minced meat substrates that had been spiked with varying concentrations of morphine. Morphine concentrations were chosen to reflect typical levels in human tissues from opiate overdose victims. After maturing on substrates, larvae were analyzed for the presence of morphine using chemiluminescence detection coupled to flow injection analysis and a rapid HPLC method. Analysis of the larval matrix by flow injection analysis with chemiluminescence detection indicated the presence of interferants capable of generating chemiluminescence. A rapid chromatographic separation with a monolithic column allowed selective determination of morphine in larvae using postcolumn chemiluminescence detection. Larvae of C. stygia reared on substrates containing morphine at concentrations of 500 and 1000 ng/g did not sequester morphine at detectable concentrations. Larvae reared on substrates containing morphine concentrations of 2500, 5000, and 10,000 ng/g tested positive for the drug at concentrations of 765, 2720, and 3010 ng/g, respectively.

President's Address: Cardiac Stimulants

An attempt is made to systematize our knowledge of certain drugs which are supposed to exercise a direct or indirect stimulating action on the heart. The actions on the circulation of strychnine, alcohol, camphor, adrenaline and pituitrin, which have been taken as representative examples, are briefly reviewed, with the object of separating out points in their actions in regard to which clinicians and pharmacologists are in general agreement, and of suggesting explanations for some of the dissensions that remain. The suggestion is made that much of the prevailing confusion in regard to the actions and uses of such drugs is due to the fact that we have as yet no sufficiently accurate classification either of "cardiac stimulants" or of "cardiac failures," wherefore it is difficult to bring a disorder and its remedy into proper alignment.