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Photochemical & Photobiological... May 2019Antimicrobial photodynamic therapy (aPDT) is a growing approach to treat skin and mucosal infections. Despite its effectiveness, investigators have explored whether aPDT...
BACKGROUND
Antimicrobial photodynamic therapy (aPDT) is a growing approach to treat skin and mucosal infections. Despite its effectiveness, investigators have explored whether aPDT can be further combined with antibiotics and antifungal drugs.
OBJECTIVE
To systematically assess the in vivo studies on the effectiveness of combinations of aPTD plus antimicrobials in the treatment of cutaneous and mucosal infections.
MATERIALS AND METHODS
Searches were performed in four databases (PubMed, EMBASE, Cochrane library databases, ClinicaTrials.gov) until July 2018. The pooled information was evaluated according to the PRISMA guidelines.
RESULTS
11 full-text articles were finally evaluated and included. The best aPDT combinations involved 5-aminolevulinic acid or phenothiazinium dye-based aPDT. In general, the combination shows benefits such as reducing treatment times, lowering drug dosages, decreasing drug toxicity, improving patient compliance and diminishing the risk of developing resistance. The mechanism of action may be that first aPDT damages the microbial cell wall or membrane, which allows better penetration of the antimicrobial drug.
LIMITATIONS
The number of studies was low, the protocols used were heterogeneous, and there was a lack of clinical trials.
CONCLUSIONS
The additive or synergistic effect of aPDT combined with antimicrobials could be promising to manage skin and mucosal infections, helping to overcome the microbial drug resistance.
Topics: Anti-Bacterial Agents; Gram-Negative Bacteria; Humans; Microbial Sensitivity Tests; Mouth Diseases; Mouth Mucosa; Photochemotherapy; Skin
PubMed: 30821303
DOI: 10.1039/c8pp00534f -
Journal of Neuro-oncology Feb 2019Differentiation of normal pituitary from abnormal tumor tissue remains a surgical challenge despite improvements in optical visualization technology for pituitary...
INTRODUCTION
Differentiation of normal pituitary from abnormal tumor tissue remains a surgical challenge despite improvements in optical visualization technology for pituitary adenoma (PA) surgery. During neurosurgical procedures for other tumor types, 5-aminolevulinic acid (5-ALA) has become a focus of investigation based on its high specificity in differentiating tumor tissue. However, the role of 5-ALA and other optical fluorescent agents in PA surgery remains less clear.
OBJECTIVE
To perform a systematic review on the use of various optical fluorescent agents in PA surgery.
METHOD
Using PRISMA guidelines, a systematic literature review to identify reports describing 5-ALA and other optical agents for fluorescence-guided surgery for PA was performed. Eleven research studies met inclusion criteria and were reviewed.
RESULTS
In two studies, 5-ALA was not shown to be effective in aiding PA resection using standard neurosurgical endoscopic/microscopic approaches. 5-ALA photodynamic therapy was evaluated in two in-vitro models with inconsistent results. Intraoperative use of indocyanine green (ICG) concluded with varying results, but showed a tendency towards improved differentiation of functional PA. OTL38 showed potential for intraoperative identification of nonfunctioning PA, particularly in tumors with high folate receptor expression. One study reported clinically useful fluorescence following sodium fluorescein administration.
CONCLUSION
We conclude that selected optical fluorescent agents, including ICG and folate receptors, are most likely to hold promise for clinical use in differentiating PA from normal tissue.
Topics: Adenoma; Aminolevulinic Acid; Fluorescent Dyes; Humans; Optical Imaging; Pituitary Neoplasms; Surgery, Computer-Assisted
PubMed: 30523607
DOI: 10.1007/s11060-018-03062-2 -
Annals of Internal Medicine Oct 2018Most interventions for basal cell carcinoma (BCC) have not been compared in head-to-head randomized trials. (Meta-Analysis)
Meta-Analysis
BACKGROUND
Most interventions for basal cell carcinoma (BCC) have not been compared in head-to-head randomized trials.
PURPOSE
To evaluate the comparative effectiveness and safety of treatments of primary BCC in adults.
DATA SOURCES
English-language searches of MEDLINE, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and Embase from inception to May 2018; reference lists of guidelines and systematic reviews; and a search of ClinicalTrials.gov in August 2016.
STUDY SELECTION
Comparative studies of treatments currently used in adults with primary BCC.
DATA EXTRACTION
One investigator extracted data on recurrence, histologic clearance, clinical clearance, cosmetic outcomes, quality of life, and mortality, and a second reviewer verified extractions. Several investigators evaluated risk of bias for each study.
DATA SYNTHESIS
Forty randomized trials and 5 nonrandomized studies compared 18 interventions in 9 categories. Relative intervention effects and mean outcome frequencies were estimated using frequentist network meta-analyses. Estimated recurrence rates were similar for excision (3.8% [95% CI, 1.5% to 9.5%]), Mohs surgery (3.8% [CI, 0.7% to 18.2%]), curettage and diathermy (6.9% [CI, 0.9% to 36.6%]), and external-beam radiation (3.5% [CI, 0.7% to 16.8%]). Recurrence rates were higher for cryotherapy (22.3% [CI, 10.2% to 42.0%]), curettage and cryotherapy (19.9% [CI, 4.6% to 56.1%]), 5-fluorouracil (18.8% [CI, 10.1% to 32.5%]), imiquimod (14.1% [CI, 5.4% to 32.4%]), and photodynamic therapy using methyl-aminolevulinic acid (18.8% [CI, 10.1% to 32.5%]) or aminolevulinic acid (16.6% [CI, 7.5% to 32.8%]). The proportion of patients reporting good or better cosmetic outcomes was better for photodynamic therapy using methyl-aminolevulinic acid (93.8% [CI, 79.2% to 98.3%]) or aminolevulinic acid (95.8% [CI, 84.2% to 99.0%]) than for excision (77.8% [CI, 44.8% to 93.8%]) or cryotherapy (51.1% [CI, 15.8% to 85.4%]). Data on quality of life and mortality were too sparse for quantitative synthesis.
LIMITATION
Data are sparse, and effect estimates are imprecise and informed by indirect comparisons.
CONCLUSION
Surgical treatments and external-beam radiation have low recurrence rates for the treatment of low-risk BCC, but substantial uncertainty exists about their comparative effectiveness versus other treatments. Gaps remain regarding high-risk BCC subtypes and important outcomes, including costs.
PRIMARY FUNDING SOURCE
Agency for Healthcare Research and Quality. (PROSPERO: CRD42016043353).
Topics: Carcinoma, Basal Cell; Humans; Network Meta-Analysis; Skin Neoplasms
PubMed: 30242379
DOI: 10.7326/M18-0678 -
The Cochrane Database of Systematic... Jan 2018Extent of resection is considered to be a prognostic factor in neuro-oncology. Intraoperative imaging technologies are designed to help achieve this goal. It is not... (Review)
Review
BACKGROUND
Extent of resection is considered to be a prognostic factor in neuro-oncology. Intraoperative imaging technologies are designed to help achieve this goal. It is not clear whether any of these sometimes very expensive tools (or their combination) should be recommended as standard care for people with brain tumours. We set out to determine if intraoperative imaging technology offers any advantage in terms of extent of resection over standard surgery and if any one technology was more effective than another.
OBJECTIVES
To establish the overall effectiveness and safety of intraoperative imaging technology in resection of glioma. To supplement this review of effects, we also wished to identify cost analyses and economic evaluations as part of a Brief Economic Commentary (BEC).
SEARCH METHODS
We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (Issue 7, 2017), MEDLINE (1946 to June, week 4, 2017), and Embase (1980 to 2017, week 27). We searched the reference lists of all identified studies. We handsearched two journals, the Journal of Neuro-Oncology and Neuro-oncology, from 1991 to 2017, including all conference abstracts. We contacted neuro-oncologists, trial authors, and manufacturers regarding ongoing and unpublished trials.
SELECTION CRITERIA
Randomised controlled trials evaluating people of all ages with presumed new or recurrent glial tumours (of any location or histology) from clinical examination and imaging (computed tomography (CT) or magnetic resonance imaging (MRI), or both). Additional imaging modalities (e.g. positron emission tomography, magnetic resonance spectroscopy) were not mandatory. Interventions included intraoperative MRI (iMRI), fluorescence-guided surgery, ultrasound, and neuronavigation (with or without additional image processing, e.g. tractography).
DATA COLLECTION AND ANALYSIS
Two review authors independently assessed the search results for relevance, undertook critical appraisal according to known guidelines, and extracted data using a prespecified pro forma.
MAIN RESULTS
We identified four randomised controlled trials, using different intraoperative imaging technologies: iMRI (2 trials including 58 and 14 participants, respectively); fluorescence-guided surgery with 5-aminolevulinic acid (5-ALA) (1 trial, 322 participants); and neuronavigation (1 trial, 45 participants). We identified one ongoing trial assessing iMRI with a planned sample size of 304 participants for which results are expected to be published around autumn 2018. We identified no trials for ultrasound.Meta-analysis was not appropriate due to differences in the tumours included (eloquent versus non-eloquent locations) and variations in the image guidance tools used in the control arms (usually selective utilisation of neuronavigation). There were significant concerns regarding risk of bias in all the included studies. All studies included people with high-grade glioma only.Extent of resection was increased in one trial of iMRI (risk ratio (RR) of incomplete resection 0.13, 95% confidence interval (CI) 0.02 to 0.96; 1 study, 49 participants; very low-quality evidence) and in the trial of 5-ALA (RR of incomplete resection 0.55, 95% CI 0.42 to 0.71; 1 study, 270 participants; low-quality evidence). The other trial assessing iMRI was stopped early after an unplanned interim analysis including 14 participants, therefore the trial provides very low-quality evidence. The trial of neuronavigation provided insufficient data to evaluate the effects on extent of resection.Reporting of adverse events was incomplete and suggestive of significant reporting bias (very low-quality evidence). Overall, reported events were low in most trials. There was no clear evidence of improvement in overall survival with 5-ALA (hazard ratio 0.83, 95% CI 0.62 to 1.07; 1 study, 270 participants; low-quality evidence). Progression-free survival data were not available in an appropriate format for analysis. Data for quality of life were only available for one study and suffered from significant attrition bias (very low-quality evidence).
AUTHORS' CONCLUSIONS
Intra-operative imaging technologies, specifically iMRI and 5-ALA, may be of benefit in maximising extent of resection in participants with high grade glioma. However, this is based on low to very low quality evidence, and is therefore very uncertain. The short- and long-term neurological effects are uncertain. Effects of image-guided surgery on overall survival, progression-free survival, and quality of life are unclear. A brief economic commentary found limited economic evidence for the equivocal use of iMRI compared with conventional surgery. In terms of costs, a non-systematic review of economic studies suggested that compared with standard surgery use of image-guided surgery has an uncertain effect on costs and that 5-aminolevulinic acid was more costly. Further research, including studies of ultrasound-guided surgery, is needed.
Topics: Aminolevulinic Acid; Brain; Brain Neoplasms; Glioma; Humans; Intraoperative Care; Magnetic Resonance Imaging; Neuronavigation; Photosensitizing Agents; Tomography, X-Ray Computed
PubMed: 29355914
DOI: 10.1002/14651858.CD012788.pub2 -
Arab Journal of Urology Jun 2017To assess the diagnostic accuracy and safety of photodynamic diagnosis (PDD) in upper urinary tract urothelial carcinoma (UUTUC). (Review)
Review
OBJECTIVE
To assess the diagnostic accuracy and safety of photodynamic diagnosis (PDD) in upper urinary tract urothelial carcinoma (UUTUC).
MATERIALS AND METHODS
A systematic literature search was conducted. Included studies were assessed for the risks of bias and quality using appropriate tools. Dedicated data extraction forms were used. Diagnostic accuracy in terms of sensitivity and specificity were quoted whenever provided by individual studies. A combined toxicity profile of 5-aminolevulinic acid (5ALA) was given after reviewing individual studies.
RESULTS
In all, 17 studies were identified. After screening seven studies were included involving a total of 194 patients. None of the studies were randomised. All the available studies were of low-to-moderate quality. The largest available study, with 106 patients, reported a sensitivity of 95.8% and 53.5% for PDD and white-light (WL) ureterorenoscopy (URS) respectively, with a statistically significant difference. The specificity was 96.6% for PDD and 95.2% for WL-URS with no statistical significance. PDD showed better ability in detecting carcinoma and dysplasia. One study compared PDD to computed tomography urogram (CTU) and found PDD to have better sensitivity and statistically significantly better specificity. 5ALA-associated toxicity was minor in nature and hypotension was the most common adverse event.
CONCLUSION
PDD in UUTUC appears to be more accurate than WL-URS and CTU, with no significant toxicity. Larger scale randomised trials are needed.
PubMed: 29071138
DOI: 10.1016/j.aju.2017.01.003 -
The British Journal of Dermatology Jan 2018We undertook a Cochrane review of randomized controlled trials (RCTs) evaluating the effects of light-based interventions for acne vulgaris. We searched the Cochrane... (Meta-Analysis)
Meta-Analysis
We undertook a Cochrane review of randomized controlled trials (RCTs) evaluating the effects of light-based interventions for acne vulgaris. We searched the Cochrane Skin Specialised Register, CENTRAL, MEDLINE, Embase, LILACS, ISI Web of Science and grey literature sources (September 2015). We used the Grading of Recommendations Assessment, Development and Evaluation Working Group approach to assess the quality of evidence (QoE). We included 71 RCTs (4211 participants, median sample size 31). Results from a single study (n = 266, low QoE) showed little or no difference in effectiveness on participants' assessment of improvement between 20% aminolaevulinic acid (ALA) photodynamic therapy (PDT), activated by blue light, vs. vehicle plus blue light, whereas another study (n = 180) comparing ALA-PDT (red light) concentrations showed that 20% ALA-PDT was no more effective than 15% ALA-PDT but better than 10% and 5% ALA-PDT. Pooled data from three studies (n = 360, moderate QoE) showed that methyl aminolaevulinate PDT, activated by red light, had a similar effect on changes in lesion counts vs. placebo cream with red light. Several studies compared yellow light with placebo or no treatment, infrared light with no treatment, gold microparticle suspension with vehicle and clindamycin/benzoyl peroxide (C/BPO) combined with pulsed dye laser with C/BPO alone. None of these showed any clinically significant effects. Most studies reported adverse effects, but inadequately, with scarring reported as absent, and blistering only in studies on intense pulsed light, infrared light and PDT (very low QoE). Carefully planned studies, using standardized outcome measures and common acne treatments as comparators, are needed.
Topics: Acne Vulgaris; Adult; Aminolevulinic Acid; Female; GRADE Approach; Gold Compounds; Humans; Infrared Rays; Male; Photochemotherapy; Photosensitizing Agents; Phototherapy; Randomized Controlled Trials as Topic; Treatment Outcome
PubMed: 28338214
DOI: 10.1111/bjd.15495 -
Acta Neurochirurgica Jan 2017Fluorescence-guided surgery (FGS) is a technique used to enhance visualization of tumor margins in order to increase the extent of tumor resection in glioma surgery. In... (Review)
Review
BACKGROUND
Fluorescence-guided surgery (FGS) is a technique used to enhance visualization of tumor margins in order to increase the extent of tumor resection in glioma surgery. In this paper, we systematically review all clinically tested fluorescent agents for application in FGS for glioma and all preclinically tested agents with the potential for FGS for glioma.
METHODS
We searched the PubMed and Embase databases for all potentially relevant studies through March 2016. We assessed fluorescent agents by the following outcomes: rate of gross total resection (GTR), overall and progression-free survival, sensitivity and specificity in discriminating tumor and healthy brain tissue, tumor-to-normal ratio of fluorescent signal, and incidence of adverse events.
RESULTS
The search strategy resulted in 2155 articles that were screened by titles and abstracts. After full-text screening, 105 articles fulfilled the inclusion criteria evaluating the following fluorescent agents: 5-aminolevulinic acid (5-ALA) (44 studies, including three randomized control trials), fluorescein (11), indocyanine green (five), hypericin (two), 5-aminofluorescein-human serum albumin (one), endogenous fluorophores (nine) and fluorescent agents in a pre-clinical testing phase (30). Three meta-analyses were also identified.
CONCLUSIONS
5-ALA is the only fluorescent agent that has been tested in a randomized controlled trial and results in an improvement of GTR and progression-free survival in high-grade gliomas. Observational cohort studies and case series suggest similar outcomes for FGS using fluorescein. Molecular targeting agents (e.g., fluorophore/nanoparticle labeled with anti-EGFR antibodies) are still in the pre-clinical phase, but offer promising results and may be valuable future alternatives.
Topics: Aminolevulinic Acid; Animals; Brain Neoplasms; Fluorescent Dyes; Glioma; Humans; Neurosurgical Procedures; Photosensitizing Agents
PubMed: 27878374
DOI: 10.1007/s00701-016-3028-5 -
The Cochrane Database of Systematic... Sep 2016Acne vulgaris is a very common skin problem that presents with blackheads, whiteheads, and inflamed spots. It frequently results in physical scarring and may cause... (Review)
Review
BACKGROUND
Acne vulgaris is a very common skin problem that presents with blackheads, whiteheads, and inflamed spots. It frequently results in physical scarring and may cause psychological distress. The use of oral and topical treatments can be limited in some people due to ineffectiveness, inconvenience, poor tolerability or side-effects. Some studies have suggested promising results for light therapies.
OBJECTIVES
To explore the effects of light treatment of different wavelengths for acne.
SEARCH METHODS
We searched the following databases up to September 2015: the Cochrane Skin Specialised Register, CENTRAL, MEDLINE, Embase and LILACS. We searched ISI Web of Science and Dissertation Abstracts International (from inception). We also searched five trials registers, and grey literature sources. We checked the reference lists of studies and reviews and consulted study authors and other experts in the field to identify further references to relevant randomised controlled trials (RCTs). We updated these searches in July 2016 but these results have not yet been incorporated into the review.
SELECTION CRITERIA
We included RCTs of light for treatment of acne vulgaris, regardless of language or publication status.
DATA COLLECTION AND ANALYSIS
We used standard methodological procedures expected by Cochrane.
MAIN RESULTS
We included 71 studies, randomising a total of 4211 participants.Most studies were small (median 31 participants) and included participants with mild to moderate acne of both sexes and with a mean age of 20 to 30 years. Light interventions differed greatly in wavelength, dose, active substances used in photodynamic therapy (PDT), and comparator interventions (most commonly no treatment, placebo, another light intervention, or various topical treatments). Numbers of light sessions varied from one to 112 (most commonly two to four). Frequency of application varied from twice daily to once monthly.Selection and performance bias were unclear in the majority of studies. Detection bias was unclear for participant-assessed outcomes and low for investigator-assessed outcomes in the majority of studies. Attrition and reporting bias were low in over half of the studies and unclear or high in the rest. Two thirds of studies were industry-sponsored; study authors either reported conflict of interest, or such information was not declared, so we judged the risk of bias as unclear.Comparisons of most interventions for our first primary outcome 'Participant's global assessment of improvement' were not possible due to the variation in the interventions and the way the studies' outcomes were measured. We did not combine the effect estimates but rated the quality of the evidence as very low for the comparison of light therapies, including PDT to placebo, no treatment, topical treatment or other comparators for this outcome. One study which included 266 participants with moderate to severe acne showed little or no difference in effectiveness for this outcome between 20% aminolevulinic acid (ALA)-PDT (activated by blue light) versus vehicle plus blue light (risk ratio (RR) 0.87, 95% confidence interval (CI) 0.72 to 1.04, low-quality evidence). A study (n = 180) of a comparison of ALA-PDT (activated by red light) concentrations showed 20% ALA was no more effective than 15% (RR 1.05, 95% CI 0.96 to 1.15) but better than 10% ALA (RR 1.22, 95% CI 1.05 to 1.42) and 5% ALA (RR 1.47, 95% CI 1.19 to 1.81). The number needed to treat for an additional beneficial outcome (NNTB) was 6 (95% CI 3 to 19) and 4 (95% CI 2 to 6) for the comparison of 20% ALA with 10% and 5% ALA, respectively.For our second primary outcome 'Investigator-assessed changes in lesion counts', we combined three RCTs, with 360 participants with moderate to severe acne and found methyl aminolevulinate (MAL) PDT (activated by red light) was no different to placebo cream plus red light with regard to change in inflamed lesions (ILs) (mean difference (MD) -2.85, 95% CI -7.51 to 1.81), percentage change in ILs (MD -10.09, 95% CI -20.25 to 0.06), change in non-inflamed lesions (NILs) (MD -2.01, 95% CI -7.07 to 3.05), or in percentage change in NILs (MD -8.09, 95% CI -21.51 to 5.32). We assessed the evidence as moderate quality for these outcomes meaning that there is little or no clinical difference between these two interventions for lesion counts.Studies comparing the effects of other interventions were inconsistent or had small samples and high risk of bias. We performed only narrative synthesis for the results of the remaining trials, due to great variation in many aspects of the studies, poor reporting, and failure to obtain necessary data. Several studies compared yellow light to placebo or no treatment, infrared light to no treatment, gold microparticle suspension to vehicle, and clindamycin/benzoyl peroxide combined with pulsed dye laser to clindamycin/benzoyl peroxide alone. There were also several other studies comparing MAL-PDT to light-only treatment, to adapalene and in combination with long-pulsed dye laser to long-pulsed dye laser alone. None of these showed any clinically significant effects.Our third primary outcome was 'Investigator-assessed severe adverse effects'. Most studies reported adverse effects, but not adequately with scarring reported as absent, and blistering reported only in studies on intense pulsed light, infrared light and photodynamic therapies. We rated the quality of the evidence as very low, meaning we were uncertain of the adverse effects of the light therapies.Although our primary endpoint was long-term outcomes, less than half of the studies performed assessments later than eight weeks after final treatment. Only a few studies assessed outcomes at more than three months after final treatment, and longer-term assessments are mostly not covered in this review.
AUTHORS' CONCLUSIONS
High-quality evidence on the use of light therapies for people with acne is lacking. There is low certainty of the usefulness of MAL-PDT (red light) or ALA-PDT (blue light) as standard therapies for people with moderate to severe acne.Carefully planned studies, using standardised outcome measures, comparing the effectiveness of common acne treatments with light therapies would be welcomed, together with adherence to the Consolidated Standards of Reporting Trials (CONSORT) guidelines.
PubMed: 27670126
DOI: 10.1002/14651858.CD007917.pub2 -
Cancer Aug 20165-Aminolevulinic acid (5-ALA) has been approved as an intraoperative adjunct in glioma surgery in Europe, but not North America. A systematic review was conducted to... (Meta-Analysis)
Meta-Analysis Review
5-Aminolevulinic acid (5-ALA) has been approved as an intraoperative adjunct in glioma surgery in Europe, but not North America. A systematic review was conducted to assess the evidence regarding 5-ALA as a surgical adjunct. The MEDLINE, EMBASE, and CENTRAL databases were searched, using terms relevant to "5-ALA" and "high-grade gliomas." Included studies were based on adults aged ≥18 years who underwent surgical resection/biopsy. No language or date limitations were used. Forty-three studies (1830 patients) were identified. Thirty-six were coordinated by European countries, 2 were in the United States, and none were in Canada. One was randomized, 28 were prospective, and 14 were retrospective. Twenty-six studies assessed the utility of 5-ALA as a diagnostic tool, 24 assessed its influence on the extent of resection (EOR), 9 assessed survival, and 22 reported adverse events. 5-ALA had high sensitivity and positive predictive value, whereas its specificity increased with additional adjuncts. The EOR increased with 5-ALA, but only progression-free survival was significantly influenced. Reporting of adverse events was not systematic. The use of 5-ALA improved tumor visualization and thus enabled a greater EOR and perhaps increased survival. However, additional adjuncts may be necessary for maximizing the specificity of resection and patient safety. Additional parameters, such as patient quality of life and health economic analyses, would be informative. Thus, additional systematic collection of prospective evidence may be necessary for the global incorporation of this potentially valuable surgical adjunct into routine practice. Cancer 2016;122:2469-78. © 2016 American Cancer Society.
Topics: Aminolevulinic Acid; Brain Neoplasms; Glioma; Humans; Intraoperative Care; Magnetic Resonance Imaging; Neoplasm Grading; Neoplasm Recurrence, Local; Postoperative Care; Reproducibility of Results; Surgery, Computer-Assisted; Treatment Outcome
PubMed: 27183272
DOI: 10.1002/cncr.30088 -
Translational Psychiatry Feb 2014Although the involvement of genetic abnormalities in autism spectrum disorders (ASD) is well-accepted, recent studies point to an equal contribution by environmental... (Review)
Review
Although the involvement of genetic abnormalities in autism spectrum disorders (ASD) is well-accepted, recent studies point to an equal contribution by environmental factors, particularly environmental toxicants. However, these toxicant-related studies in ASD have not been systematically reviewed to date. Therefore, we compiled publications investigating potential associations between environmental toxicants and ASD and arranged these publications into the following three categories: (a) studies examining estimated toxicant exposures in the environment during the preconceptional, gestational and early childhood periods; (b) studies investigating biomarkers of toxicants; and (c) studies examining potential genetic susceptibilities to toxicants. A literature search of nine electronic scientific databases through November 2013 was performed. In the first category examining ASD risk and estimated toxicant exposures in the environment, the majority of studies (34/37; 92%) reported an association. Most of these studies were retrospective case-control, ecological or prospective cohort studies, although a few had weaker study designs (for example, case reports or series). Toxicants implicated in ASD included pesticides, phthalates, polychlorinated biphenyls (PCBs), solvents, toxic waste sites, air pollutants and heavy metals, with the strongest evidence found for air pollutants and pesticides. Gestational exposure to methylmercury (through fish exposure, one study) and childhood exposure to pollutants in water supplies (two studies) were not found to be associated with ASD risk. In the second category of studies investigating biomarkers of toxicants and ASD, a large number was dedicated to examining heavy metals. Such studies demonstrated mixed findings, with only 19 of 40 (47%) case-control studies reporting higher concentrations of heavy metals in blood, urine, hair, brain or teeth of children with ASD compared with controls. Other biomarker studies reported that solvent, phthalate and pesticide levels were associated with ASD, whereas PCB studies were mixed. Seven studies reported a relationship between autism severity and heavy metal biomarkers, suggesting evidence of a dose-effect relationship. Overall, the evidence linking biomarkers of toxicants with ASD (the second category) was weaker compared with the evidence associating estimated exposures to toxicants in the environment and ASD risk (the first category) because many of the biomarker studies contained small sample sizes and the relationships between biomarkers and ASD were inconsistent across studies. Regarding the third category of studies investigating potential genetic susceptibilities to toxicants, 10 unique studies examined polymorphisms in genes associated with increased susceptibilities to toxicants, with 8 studies reporting that such polymorphisms were more common in ASD individuals (or their mothers, 1 study) compared with controls (one study examined multiple polymorphisms). Genes implicated in these studies included paraoxonase (PON1, three of five studies), glutathione S-transferase (GSTM1 and GSTP1, three of four studies), δ-aminolevulinic acid dehydratase (one study), SLC11A3 (one study) and the metal regulatory transcription factor 1 (one of two studies). Notably, many of the reviewed studies had significant limitations, including lack of replication, limited sample sizes, retrospective design, recall and publication biases, inadequate matching of cases and controls, and the use of nonstandard tools to diagnose ASD. The findings of this review suggest that the etiology of ASD may involve, at least in a subset of children, complex interactions between genetic factors and certain environmental toxicants that may act synergistically or in parallel during critical periods of neurodevelopment, in a manner that increases the likelihood of developing ASD. Because of the limitations of many of the reviewed studies, additional high-quality epidemiological studies concerning environmental toxicants and ASD are warranted to confirm and clarify many of these findings.
Topics: Child Development Disorders, Pervasive; Gene-Environment Interaction; Hazardous Substances; Humans
PubMed: 24518398
DOI: 10.1038/tp.2014.4