CRISPR-based gene editing of non-homologous end joining factors biases DNA repair pathway choice toward single-strand annealing in Aedes aegypti

To maintain genome stability, eukaryotic cells orchestrate DNA repair pathways to process DNA double-strand breaks (DSBs) that result from diverse developmental or environmental stimuli. Bias in the selection of DSB repair pathways, either non-homologous end joining (NHEJ) or homology-directed repair (HDR), is also critical for efficient gene editing and for homing-based gene drive approaches developed for the control of disease-transmitting vector mosquitoes. However, little is understood about DNA repair homeostasis in the mosquito genome. Here, we utilized CRISPR/Cas9 to generate indel mutant strains for core NHEJ factors ku80, DNA ligase IV (lig4), and DNA-PKcs in the mosquito Aedes aegypti and evaluated the corresponding effects on DNA repair. In a plasmid-based assay, disruption of ku80 or lig4, but not DNA-PKcs, reduced both NHEJ and SSA. However, a transgenic reporter strain-based test revealed that those mutations significantly biased DNA repair events toward SSA. Interestingly, ku80 mutation also significantly increased the end joining rate by a yet-characterized mechanism in males. Our study provides evidence that the core NHEJ factors have an antagonistic effect on SSA-based DSB repair of the Ae. aegypti genome. Down-modulating the NHEJ pathway can enhance the efficiency of nuclease-based genetic control approaches, as most of those operate by homology-based repair processes along with extensive DNA end resection that is antagonized by NHEJ.

Functional Laryngeal Assessment in Patients with Tracheostomy Following COVID-19 a Prospective Cohort Study

To explore laryngeal function of tracheostomised patients with COVID-19 in the acute phase, to identify ways teams may facilitate and expedite tracheostomy weaning and rehabilitation of upper airway function. Consecutive tracheostomised patients underwent laryngeal examination during mechanical ventilation weaning. Primary outcomes included prevalence of upper aerodigestive oedema and airway protection during swallow, tracheostomy duration, ICU frailty scores, and oral intake type. Analyses included bivariate associations and exploratory multivariable regressions. 48 consecutive patients who underwent tracheostomy insertion as part of their respiratory wean following invasive ventilation in a single UK tertiary hospital were included. 21 (43.8%) had impaired airway protection on swallow (PAS ≥ 3) with 32 (66.7%) having marked airway oedema in at least one laryngeal area. Impaired airway protection was associated with longer total artificial airway duration (p = 0.008), longer tracheostomy tube duration (p = 0.007), multiple intubations (p = 0.006) and was associated with persistent ICU acquired weakness at ICU discharge (p = 0.03). Impaired airway protection was also an independent predictor for longer tracheostomy tube duration (p = 0.02, Beta 0.38, 95% CI 2.36 to 27.16). The majority of our study patients presented with complex laryngeal findings which were associated with impaired airway protection. We suggest a proactive standardized scoring and review protocol to manage this complex group of patients in order to maximize health outcomes and ICU resources. Early laryngeal assessment may facilitate weaning from invasive mechanical ventilation and liberation from tracheostomy, as well as practical and objective risk stratification for patients regarding decannulation and feeding.

Engineering a self-eliminating transgene in the yellow fever mosquito, Aedes aegypti

Promising genetics-based approaches are being developed to reduce or prevent the transmission of mosquito-vectored diseases. Less clear is how such transgenes can be removed from the environment, a concern that is particularly relevant for highly invasive gene drive transgenes. Here, we lay the groundwork for a transgene removal system based on single-strand annealing (SSA), a eukaryotic DNA repair mechanism. An SSA-based rescuer strain (kmo^RG ) was engineered to have direct repeat sequences (DRs) in the Aedes aegypti kynurenine 3-monooxygenase (kmo) gene flanking the intervening transgenic cargo genes, DsRED and EGFP. Targeted induction of DNA double-strand breaks (DSBs) in the DsRED transgene successfully triggered complete elimination of the entire cargo from the kmo^RG strain, restoring the wild-type kmo gene, and thereby, normal eye pigmentation. Our work establishes the framework for strategies to remove transgene sequences during the evaluation and testing of modified strains for genetics-based mosquito control.

Sinecatechins ointment as a potential novel treatment for usual type vulval intraepithelial neoplasia: a single-centre double-blind randomised control study

OBJECTIVE

To compare the safety and efficacy of 10% sinecatechins (Veregen® ) ointment against placebo in the treatment of usual type vulvar intraepithelial neoplasia (uVIN).

DESIGN

A Phase II double-blind randomised control trial.

SETTING

A tertiary gynaecological oncology referral centre.

POPULATION

All women diagnosed with primary and recurrent uVIN.

METHODS

Eligible patients were randomised 1:1 to receive either sinecatechins or placebo ointment (applied three times daily for 16 weeks) and were followed up at 2, 4, 8, 16, 32 and 52 weeks.

MAIN OUTCOME MEASURES

The primary outcome measure, recorded at 16 and 32 weeks, was histological response (HR). Secondary outcome measures included clinical (CR) response, toxicity, quality of life and pain scores.

RESULTS

There was no observed difference in HR between the two arms. However, of the 26 patients who were randomised, all 13 patients who received sinecatechins showed either complete (n = 5) or partial (n = 8) CR, when best CR was evaluated. In placebo group, three patients had complete CR, two had partial CR, six had stable disease and two were lost to follow up. Patients in the sinecatechins group showed a statistically significant improvement in best observed CR as compared with the placebo group (P = 0.002). There was no difference in toxicity reported in either group.

CONCLUSION

Although we did not observe a difference in HR between the two treatment arms, we found that 10% sinecatechins application is safe and shows promise in inducing clinical resolution of uVIN lesions and symptom improvement, thus warranting further investigation in a larger multicentre study.

TWEETABLE ABSTRACT

A randomised control study indicating that sinecatechins ointment may be a novel treatment for uVIN.

A knockout screen of genes expressed specifically in Ae. aegypti pupae reveals a critical role for stretchin in mosquito flight

Aedes aegypti is a critical vector for transmitting Zika, dengue, chikungunya, and yellow fever viruses to humans. Genetic strategies to limit mosquito survival based upon sex distortion or disruption of development may be valuable new tools to control Ae. aegypti populations. We identified six genes with expression limited to pupal development; osi8 and osi11 (Osiris protein family), CPRs and CPF (cuticle protein family), and stretchin (a muscle protein). Heritable CRISPR/Cas9-mediated gene knockout of these genes did not reveal any defects in pupal development. However, stretchin-null mutations (strn^Δ35/Δ41) resulted in flightless mosquitoes with an abnormal open wing posture. The inability of adult strn^Δ35/Δ41 mosquitoes to fly restricted their escape from aquatic rearing media following eclosion, and substantially reduced adult survival rates. Transgenic strains which contain the EGFP marker gene under the control of strn regulatory regions (0.8 kb, 1.4 kb, and 2.2 kb upstream, respectively), revealed the gene expression pattern of strn in muscle-like tissues in the thorax during late morphogenesis from L₄ larvae to young adults. We demonstrated that Ae. aegypti pupae-specific strn is critical for adult mosquito flight capability and a key late-acting lethal target for mosquito-borne disease control.

Dysphagia presentation and management following COVID-19: an acute care tertiary centre experience

OBJECTIVES

As the pathophysiology of COVID-19 emerges, this paper describes dysphagia as a sequela of the disease, including its diagnosis and management, hypothesised causes, symptomatology in relation to viral progression, and concurrent variables such as intubation, tracheostomy and delirium, at a tertiary UK hospital.

RESULTS

During the first wave of the COVID-19 pandemic, 208 out of 736 patients (28.9 per cent) admitted to our institution with SARS-CoV-2 were referred for swallow assessment. Of the 208 patients, 102 were admitted to the intensive treatment unit for mechanical ventilation support, of which 82 were tracheostomised. The majority of patients regained near normal swallow function prior to discharge, regardless of intubation duration or tracheostomy status.

CONCLUSION

Dysphagia is prevalent in patients admitted either to the intensive treatment unit or the ward with COVID-19 related respiratory issues. This paper describes the crucial role of intensive swallow rehabilitation to manage dysphagia associated with this disease, including therapeutic respiratory weaning for those with a tracheostomy.

Pigmentary keratitis in pugs in the United Kingdom: prevalence and associated features

Background

Pigmentary keratitis (PK) is commonly recognised in Pugs, but its aetiology is not completely understood. The aim of this study was to determine the prevalence and associated features of PK in Pugs in the United Kingdom (UK).

Results

A total of 210 Pugs (420 eyes) were recruited from 12 UK dog shows and social events. The median age of Pugs recruited was 2.50 years (range 0.25–16.25 years). Pigmentary keratitis was detected in 369/420 (87.8%) eyes and in at least one eye 193/210 (91.9%) Pugs, of which 17/193 (8.8%) were affected unilaterally and 176/193 (91.2%) bilaterally. Pigmentary keratitis was typically mild to moderate (46.3 and 49.9% of eyes, respectively). Detection of PK was significantly associated with increased age (P = 0.002) and the presence of medial entropion of the lower eyelid (MELE) (P = 0.001). Severity of PK was significantly associated with the grade of MELE (P < 0.001). There was also a correlation between the presence of limbal pigment and PK (P = 0.036) that warrants further study.

Conclusions

This study estimated a high disease prevalence of PK in UK Pugs, and demonstrated significant associations with age and the presence of MELE. These associations, which have not been previously reported, offer an insight into the underlying pathophysiology of this condition in Pugs. The results encourage further population research, such as prospective longitudinal studies. These findings also support the development of clinical and breeding strategies based on the reduction of MELE and, possibly, limbal pigment.

The natural history of classic galactosemia: lessons from the GalNet registry

BACKGROUND

Classic galactosemia is a rare inborn error of carbohydrate metabolism, caused by a severe deficiency of the enzyme galactose-1-phosphate uridylyltransferase (GALT). A galactose-restricted diet has proven to be very effective to treat the neonatal life-threatening manifestations and has been the cornerstone of treatment for this severe disease. However, burdensome complications occur despite a lifelong diet. For rare diseases, a patient disease specific registry is fundamental to monitor the lifespan pathology and to evaluate the safety and efficacy of potential therapies. In 2014, the international Galactosemias Network (GalNet) developed a web-based patient registry for this disease, the GalNet Registry. The aim was to delineate the natural history of classic galactosemia based on a large dataset of patients.

METHODS

Observational data derived from 15 countries and 32 centers including 509 patients were acquired between December 2014 and July 2018.

RESULTS

Most affected patients experienced neonatal manifestations (79.8%) and despite following a diet developed brain impairments (85.0%), primary ovarian insufficiency (79.7%) and a diminished bone mineral density (26.5%). Newborn screening, age at onset of dietary treatment, strictness of the galactose-restricted diet, p.Gln188Arg mutation and GALT enzyme activity influenced the clinical picture. Detection by newborn screening and commencement of diet in the first week of life were associated with a more favorable outcome. A homozygous p.Gln188Arg mutation, GALT enzyme activity of ≤ 1% and strict galactose restriction were associated with a less favorable outcome.

CONCLUSION

This study describes the natural history of classic galactosemia based on the hitherto largest data set.

Significant polyp and early colorectal cancer - SPECC: The role of the Colorectal Cancer Clinical Nurse Specialist (CNS): promoting patient-centred care

AIMS

The colorectal Clinical Nurse Specialist (CNS) makes an important contribution to the care of individuals diagnosed with a significant polyp and early colorectal cancer (SPECC).

METHODS

This paper offers an expert opinion on the role of the CNS in SPECC, informed by relevant literature.

RESULTS

A CNS can support the patient through the diagnostic and treatment pathway acting as the patient's advocate as a core member of the multidisciplinary team. They will offer support and information to help patients understand their diagnosis, make choices about their available treatment options and help them to feel prepared for any treatment undertaken.

CONCLUSION

By providing care that is respectful of, and responsive to, individual patient preferences, needs and values, the CNS can play an important role in promoting patient-centred care.

Evidence for causal top-down frontal contributions to predictive processes in speech perception

Perception relies on the integration of sensory information and prior expectations. Here we show that selective neurodegeneration of human frontal speech regions results in delayed reconciliation of predictions in temporal cortex. These temporal regions were not atrophic, displayed normal evoked magnetic and electrical power, and preserved neural sensitivity to manipulations of sensory detail. Frontal neurodegeneration does not prevent the perceptual effects of contextual information; instead, prior expectations are applied inflexibly. The precision of predictions correlates with beta power, in line with theoretical models of the neural instantiation of predictive coding. Fronto-temporal interactions are enhanced while participants reconcile prior predictions with degraded sensory signals. Excessively precise predictions can explain several challenging phenomena in frontal aphasias, including agrammatism and subjective difficulties with speech perception. This work demonstrates that higher-level frontal mechanisms for cognitive and behavioural flexibility make a causal functional contribution to the hierarchical generative models underlying speech perception.

The influence of hydroalcoholic media on the performance of Grewia polysaccharide in sustained release tablets

Co-administration of drugs with alcohol can affect the plasma concentration of drugs in patients. It is also known that the excipients used in the formulation of drugs may not always be resistant to alcohol. This study evaluates effect of varying alcohol concentrations on theophylline release from two grades of Grewia mollis polysaccharides. X-ray microtomography showed that native polysaccharide formulation compacts were not homogenous after the mixing process resulting in its failure in swelling studies. Removal of starch from the native polysaccharide resulted in homogenous formulation compacts resistant to damage in high alcoholic media in pH 6.8 (40%v/v absolute ethanol). Destarched polymer compacts had a significantly higher hardness (375N) than that of the native polysaccharide (82N) and HPMC K4M (146N). Dissolution studies showed similarity at all levels of alcohol tested (f₂=57-91) in simulated gastric media (pH 1.2). The dissolution profiles in the simulated intestinal fluids were also similar (f₂=60-94), with the exception of the native polysaccharide in pH 6.8 (40%v/v absolute ethanol) (f₂=43). This work highlights the properties of Grewia polysaccharide as a matrix former that can resist high alcoholic effects therefore; it may be suitable as an alternative to some of the commercially available matrix formers with wider applications for drug delivery as a cheaper alternative in the developing world.

Intra- and inter-observer reproducibility of CINtec® PLUS in ThinPrep® cytology preparations

BACKGROUND

This study evaluated the intra- and inter-observer reproducibility of the dual-stain biomarker, CINtec^® PLUS cytology in ThinPrep^® specimens, for improved specificity in the detection of cervical disease in women testing human papillomavirus (HPV) positive.

METHODS

A total of 972 cases of HPV-positive women from a triage and primary HPV screening population were selected from an ongoing study evaluating the clinical performance of CINtec^® PLUS cytology. For reproducibility analyses, three cytotechnologists rescreened sets of slides which they had previously reported themselves and which were previously reported by each of the other cytotechnologists. The original results of slides previously screened by each of the three cytotechnologists were also compared with the results of an expert reference evaluator.

RESULTS

Intra- and inter-observer agreement for paired evaluations between reviewers ranged from 82.8% to 94.9% (kappa 0.65-0.91) and 89.2% to 93% (kappa 0.83-0.88), respectively. Reproducibility analyses between the cytotechnologists and the reference evaluator revealed agreements ranging from 95.5% to 98% (kappa 0.89-0.96).

CONCLUSION

Evaluation of the dual-stain biomarker showed a high level of agreement across all evaluators suggesting that CINtec^® PLUS cytology will perform well in the hands of cytotechnologists and pathologist reviewers and could be introduced into cellular pathology laboratories that employ ThinPrep^® LBC with a minimum effort.

Definition and solution of a stochastic inverse problem for the Manning's n parameter field in hydrodynamic models

The uncertainty in spatially heterogeneous Manning's n fields is quantified using a novel formulation and numerical solution of stochastic inverse problems for physics-based models. The uncertainty is quantified in terms of a probability measure and the physics-based model considered here is the state-of-the-art ADCIRC model although the presented methodology applies to other hydrodynamic models. An accessible overview of the formulation and solution of the stochastic inverse problem in a mathematically rigorous framework based on measure theory is presented. Technical details that arise in practice by applying the framework to determine the Manning's n parameter field in a shallow water equation model used for coastal hydrodynamics are presented and an efficient computational algorithm and open source software package are developed. A new notion of "condition" for the stochastic inverse problem is defined and analyzed as it relates to the computation of probabilities. This notion of condition is investigated to determine effective output quantities of interest of maximum water elevations to use for the inverse problem for the Manning's n parameter and the effect on model predictions is analyzed.

Neural substrates of inhibitory control deficits in 22q11.2 deletion syndrome

22q11.2 deletion syndrome (22q11DS) is associated with elevated levels of impulsivity, inattention, and distractibility, which may be related to underlying neurobiological dysfunction due to haploinsufficiency for genes involved in dopaminergic neurotransmission (i.e. catechol-O-methyltransferase). The Stop-signal task has been employed to probe the neural circuitry involved in response inhibition (RI); findings in healthy individuals indicate that a fronto-basal ganglia network underlies successful inhibition of a prepotent motor response. However, little is known about the neurobiological substrates of RI difficulties in 22q11DS. Here, we investigated this using functional magnetic resonance imaging while 45 adult participants (15 22q11DS patients, 30 matched controls) performed the Stop-signal task. Healthy controls showed significantly greater activation than 22q11DS patients within frontal cortical and basal ganglia regions during successful RI, whereas 22q11DS patients did not show increased neural activity relative to controls in any regions. Using the Barratt Impulsivity Scale, we also investigated whether neural dysfunction during RI was associated with cognitive impulsivity in 22q11DS patients. RI-related activity within left middle frontal gyrus and basal ganglia was associated with severity of self-reported cognitive impulsivity. These results suggest reduced engagement of RI-related brain regions in 22q11DS patients, which may be relevant to characteristic behavioral manifestations of the disorder.

Density of mechanisms within the flexibility window of zeolites

By treating idealized zeolite frameworks as periodic mechanical trusses, we show that the number of flexible folding mechanisms in zeolite frameworks is strongly peaked at the minimum density end of their flexibility window. 25 of the 197 known zeolite frameworks exhibit an extensive flexibility, where the number of unique mechanisms increases linearly with the volume when long wavelength mechanisms are included. Extensively flexible frameworks therefore have a maximum in configurational entropy, as large crystals, at their lowest density. Most real zeolites do not exhibit extensive flexibility, suggesting that surface and edge mechanisms are important, likely during the nucleation and growth stage. The prevalence of flexibility in real zeolites suggests that, in addition to low framework energy, it is an important criterion when searching large databases of hypothetical zeolites for potentially useful realizable structures.

η and η' mesons from lattice QCD

The large mass of the ninth pseudoscalar meson, the η', is believed to arise from the combined effects of the axial anomaly and the gauge field topology present in QCD. We report a realistic, 2+1-flavor, lattice QCD calculation of the η and η' masses and mixing which confirms this picture. The physical eigenstates show small octet-singlet mixing with a mixing angle of θ=-14.1(2.8)°. Extrapolation to the physical light quark mass gives, with statistical errors only, mη=573(6) MeV and mη'=947(142) MeV, consistent with the experimental values of 548 and 958 MeV.

Bilateral temporomandibular joint dislocation following pulmonary function testing: a case report and review of closed reduction techniques

Temporomandibular joint dislocation is not a common presentation to the emergency department but it is one that requires prompt diagnosis and reduction. This is thought to be the first reported case of spontaneous bilateral temporomandibular joint dislocation after routine pulmonary function testing. The management of the case is discussed and a review of closed reduction techniques commonly used in the emergency department is presented.

Bilateral temporomandibular joint dislocation following pulmonary function testing: a case report and review of closed reduction techniques

Temporomandibular joint (TMJ) dislocation is not a common presentation to the emergency department (ED) but one that requires prompt diagnosis and reduction. This is the first reported case of spontaneous bilateral TMJ dislocation after routine pulmonary function testing. The management of the case is discussed and a review of closed reduction techniques commonly used in the ED is presented.

Neutral-kaon mixing from (2+1)-flavor domain-wall QCD

We present the first results for neutral-kaon mixing using (2+1)-flavors of domain-wall fermions. A new approach is used to extrapolate to the physical up and down quark masses from our numerical studies with pion masses in the range 240-420 MeV; only SU(2)_{L}xSU(2)_{R} chiral symmetry is assumed and the kaon is not assumed to be light. Our main result is B_{K};{MS[over ]}(2 GeV)=0.524(10)(28) where the first error is statistical and the second incorporates estimates for all systematic errors.

Desmosomes: a role in cancer?

Much evidence now attests to the importance of desmosomes and their constituents in cancer. Alterations in the expression of desmosomal components could contribute to the progression of the disease by modifying intracellular signal transduction pathways and/or by causing reduced cell adhesion. The Wnt/beta-catenin pathway is a potential target because of the involvement of the cytoplasmic desmosomal protein plakoglobin. Loss of desmosomal adhesion is a prerequisite for the epithelial-mesenchymal transition, implicated in the conversion of early stage tumours to invasive cancers.

Antioxidant effects of herbal therapies used by patients with inflammatory bowel disease: an in vitro study

BACKGROUND

Herbal remedies used by patients for treatment of inflammatory bowel disease include slippery elm, fenugreek, devil's claw, Mexican yam, tormentil and wei tong ning, a traditional Chinese medicine. Reactive oxygen metabolites produced by inflamed colonic mucosa may be pathogenic. Aminosalicylates (5-ASA) are antioxidant and other such agents could be therapeutic.

AIMS

To assess the antioxidant effects of herbal remedies in cell-free oxidant-generating systems and inflamed human colorectal biopsies.

METHODS

Luminol-enhanced chemiluminescence in a xanthine/xanthine oxidase cell-free system was used to detect superoxide scavenging by herbs and 5-ASA, and fluorimetry to define peroxyl radical scavenging using a phycoerythrin degradation assay. Chemiluminescence was used to detect herbal effects on generation of oxygen radicals by mucosal biopsies from patients with active ulcerative colitis.

RESULTS

Like 5-ASA, all herbs, except fenugreek, scavenged superoxide dose-dependently. All materials tested scavenged peroxyl dose-dependently. Oxygen radical release from biopsies was reduced after incubation in all herbs except Mexican yam, and by 5-ASA.

CONCLUSIONS

All six herbal remedies have antioxidant effects. Fenugreek is not a superoxide scavenger, while Mexican yam did not inhibit radical generation by inflamed biopsies. Slippery elm, fenugreek, devil's claw, tormentil and wei tong ning merit formal evaluation as novel therapies in inflammatory bowel disease.

Incidence of Helicobacter pylori in patients with interstitial cystitis

OBJECTIVE

Chronic gastritis has compelling similarities to interstitial cystitis (IC). It is characterised by chronic pain in a tubular organ. Histologically, epithelial damage, inflammatory response in the lamina propria and epithelial ulcerations are seen. An infective cause was rarely considered until the emergence of Helicobacter pylori over the past 15 years. We have had experience of patients with bladder pain and irritability reporting improvement with antihistamines. It has also been reported that IC symptoms improved dramatically after treatment for H. pylori infection. Previous studies have determined the incidence of H. pylori antibodies in women with IC but we examined bladder material histologically and performed the Campylobacter-like organism (CLO) test on the biopsy specimens.

MATERIALS AND METHODS

A prospective controlled study was performed. Patients with urinary symptoms fulfilling the National Institute of Diabetes and Digestive and Kidney Diseases criteria for IC underwent GA cystoscopy at which the macroscopic appearance of the bladder was noted and biopsies were taken. The biopsy material underwent histological examination and CLO test. Control patients who were undergoing cystoscopy for reasons other than investigation of IC also had biopsy taken and the CLO test was performed on these specimens.

RESULTS

Five of 15 patients with symptoms and signs of IC had a positive CLO test. Three of 15 patients of the control group had a positive CLO test. With the 2-sided chi(2) test there was no statistical difference between the 2 groups.

CONCLUSION

Our small prospective control study does not support the hypothesis that H. pylori is an important component in the pathogenesis of interstitial cystitis.

House dust mite and cockroach exposure are strong risk factors for positive allergy skin test responses in the Childhood Asthma Management Program

BACKGROUND

Children with asthma have a high prevalence of environmental allergies, especially to indoor allergens. The relationships of exposure to indoor allergens (dust mites, cat, dog, cockroach, and molds) and other host factors to allergy sensitization have not been evaluated simultaneously in a large cohort.

OBJECTIVES

We studied 1041 children aged 5 to 12 years with mild-to-moderate asthma to determine risk factors associated with having positive allergy skin test responses to indoor allergens. Also, we described, compared, and contrasted 6 allergens in the home environments of these children from 8 North American cities.

METHODS

Data were used from baseline visits of the Childhood Asthma Management Program. Patients' sensitivities to house dust mites (Dermatophagoides farinae and Dermatophagoides pteronyssinus), cats, dogs, cockroaches, and molds were examined for relationships to demographic variables, home dust allergen exposures, number of other positive allergy skin test responses, total serum IgE levels, and smoking in the home.

RESULTS

San Diego (78.5%) and Toronto (59.3%) had the topmost percentages of homes with moderate-to-high house dust mite levels. Boston (21.5%), St Louis (16.3%), and Baltimore (13.4%) had the highest percentages of homes with detectable levels of cockroach allergen. For house dust mites, the higher the level of allergen exposure, the more likely patients were to have positive allergy skin test responses, with relative odds of 9.0 (95% confidence interval, 5.4-15.1) for those exposed to high mite levels (>10.0 microg/g dust) relative to those unexposed. Even exposure to low levels of mite allergen (0.020-2.0 microg/g) was found to be a significant risk factor for sensitization. For cockroach allergen, those with detectable home exposure were more likely to have positive skin test responses (relative odds, 2.2; 95% confidence interval, 1.3-3.8) than those with undetectable exposure. In contrast, levels of exposure to cat, dog, and mold allergens were not related to sensitization rates. For cat allergen, this may reflect lower rates of cat ownership among highly sensitized subjects. Furthermore, the number of allergy skin test responses that were positive, excluding the test for the outcome of interest for each model, and total serum IgE levels were strong independent predictors of sensitization.

CONCLUSIONS

Levels of exposure determined by house dust analysis are important determinants of sensitization for dust mite and cockroach allergen. This relationship was not demonstrable for cat, dog, or mold allergens, possibly because of confounding factors. For all allergens studied, the degree of atopy, determined by the total number of positive skin test responses or by total serum IgE levels, is an important contributing risk factor for sensitization.