Safety and feasibility pilot study of continuous low-dose maternal supplemental oxygen in fetal single ventricle heart disease.

OBJECTIVES: Fetuses with single ventricle physiology (SVP) exhibit reductions in fetal cerebral oxygenation with associated delays in fetal brain growth and neurodevelopmental outcomes. Maternal supplemental oxygen (MSO) has been proposed to improve fetal brain growth but current evidence on dosing, candidacy, and outcomes are limited. In this pilot study, we evaluated the safety and feasibility of continuous low-dose MSO in the setting of SVP. METHODS: This single-centre, open-label, pilot phase 1 safety and feasibility clinical trial included 25 pregnant individuals with a fetal diagnosis of SVP. Participants self-administered continuous supplemental oxygen using medical-grade oxygen concentrators for up to 24 hours per day from the second half of gestation until delivery. The primary aim was the evaluation of the safety profile and feasibility of MSO. A secondary preliminary analysis was performed to assess the impact of MSO on the fetal circulation by echocardiography and late-gestational cardiovascular magnetic resonance, early outcomes including brain growth and pre-operative brain injury, and 18-month neurodevelopmental outcomes by the Bayley Scales of Infant and Toddler Development 3rd Edition compared to a contemporary fetal SVP cohort that received standard of care (SOC). RESULTS: Among 25 participants, the average maternal age at conception was 35 years, and fetal SVP diagnoses included 16 right ventricle dominant, 8 left ventricle dominant, and 1 indeterminant ventricular morphology. Participants started the trial at approximately 29.3 gestational weeks and took MSO for a median 16.1 hours per day for 63 days, cumulating a median 1029 hours of oxygen intake from enrollment until delivery. The only treatment-associated adverse events were nasal complications that were typically resolved by attaching a humidifier unit to the oxygen concentrator. No premature closure of the ductus arteriosus or unexpected fetal demise was observed. In the secondary analysis, MSO was not associated with any changes in fetal growth, middle cerebral artery pulsatility index, cerebroplacental ratio, nor head circumference to abdominal circumference ratio Z-scores over gestation compared to SOC. Although MSO was associated with changes in umbilical artery pulsatility index Z-score over gestation compared to SOC (p=0.02), this was likely due to initial baseline differences in placental resistance. At late-gestational cardiovascular magnetic resonance, MSO was not associated with any significant increase in umbilical vein oxygen saturation, fetal oxygen delivery, or fetal cerebral oxygen delivery. Similarly, we observed no differences in newborn outcomes including brain volume and pre-operative brain injury, nor mortality by 18 months of age, nor neurodevelopmental outcomes at 18 months of age. CONCLUSIONS: This pilot phase 1 clinical trial indicates low-dose maternal supplemental oxygen therapy is safe and well tolerated in pregnancies diagnosed with fetal SVP. However, our protocol was not associated with any significant changes in fetal circulatory physiology or improvements in early neurologic or neurodevelopmental outcomes. This article is protected by copyright. All rights reserved.

Trends in occupational respiratory conditions with short latency in the UK.

BACKGROUND: Occupational short-latency respiratory disease (SLRD; predominantly asthma, rhinitis, hypersensitivity pneumonitis, and occupational infections) prevalence is difficult to determine but certain occupations may be associated with increased susceptibility. AIMS: This study aimed to examine which occupations and industries are currently at high risk for SLRD and determine their respective suspected causal agents. METHODS: SLRD cases reported to the SWORD scheme between 1999 and 2019 were analysed to determine directly standardized rate ratios (SRR) by occupation against the average rate for all other occupations combined. RESULTS: 'Bakers and flour confectioners' and 'vehicle spray painters' showed significantly raised SRR for SLRD in general, mostly due to occupational rhinitis (234.4; 95% CI 200.5-274.0) and asthma (63.5; 95% CI 51.5-78.3), respectively. Laboratory technicians also showed significantly raised SRR for occupational rhinitis (18.7; 95% CI 15.1-23.1), primarily caused by laboratory animals and insects. Metal machining setters and setter-operators showed increased SRR for occupational hypersensitivity pneumonitis (42.0; 95% CI 29.3-60.3), largely due to cutting/soluble oils. The occupation mostly affected by infectious disease was welding trades (12.9; 95% CI 5.7-29.3), mainly attributable to microbial pathogenicity. CONCLUSIONS: This study identified the occupational groups at increased risk of developing an SLRD based on data recorded over a recent two-decade period in the UK. Occupational asthma and rhinitis were identified as the prevailing conditions and hypersensitivity pneumonitis as a potentially rising respiratory problem in the metalworking industry.

Skin and respiratory ill-health attributed to occupational face mask use.

BACKGROUND: Face mask use in the workplace has become widespread since the onset of the Covid-19 pandemic and has been anecdotally linked to adverse health consequences. AIMS: To examine reports of adverse health consequences of occupational face mask use received by The Health and Occupation Research (THOR) network before and after the pandemic onset. METHODS: THOR databases were searched to identify all cases of ill-health attributed to 'face mask' or similar suspected causative agent between 1 January 2010 and 30 June 2021. RESULTS: Thirty two cases were identified in total, 18 reported by occupational physicians and 14 by dermatologists. Seventy-five per cent of cases were reported after the pandemic onset and 91% cases were in the health and social care sector. 25 of the 35 (71%) diagnoses were dermatological, the most frequent diagnoses being contact dermatitis (14 cases) and folliculitis/acne (6 cases). Of the seven respiratory diagnoses, four were exacerbation of pre-existing asthma. CONCLUSIONS: There is evidence of an abrupt increase in reports of predominantly dermatological ill-health attributed to occupational face mask use since the start of the pandemic. Respiratory presentations have also occurred.

Inadvertent irreversible closure of arterial duct following therapeutic use of transplacental indomethacin in a fetus with severe Ebstein's anomaly and circular shunt.

We report on a fetal case of Ebstein's anomaly with severe tricuspid regurgitation, functional pulmonary atresia and progressive circular shunting (CS) across a widely patent ductus arteriosus (DA) and regurgitant pulmonary valve, contributing to significant systemic hypoperfusion. To mitigate the extent of CS and allow the pregnancy to continue, maternal non-steroidal anti-inflammatory drug (NSAID) therapy with indomethacin was started at 33 + 5 weeks to induce DA constriction. Rather than achieving the desired narrowing of the DA, the treatment led to its complete closure and only minimal antegrade flow across the pulmonary valve. While closure of the DA resulted in the anticipated improvement in fetal hemodynamics, at birth, the child was at risk of severe hypoxemia and its consequences due to the lack of adequate pulmonary perfusion. Reduction and eventual discontinuation of the NSAID treatment did not result in DA reopening. Our experience illustrates the risk of unintended irreversible DA closure when NSAIDs are used to treat CS. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

MRI characterization of hemodynamic patterns of human fetuses with cyanotic congenital heart disease.

OBJECTIVES: To characterize, using magnetic resonance imaging (MRI), the distribution of blood flow and oxygen transport in human fetuses with subtypes of congenital heart disease (CHD) that present with neonatal cyanosis. METHODS: Blood flow was measured in the major vessels of 152 late-gestation human fetuses with CHD and 40 gestational-age-matched normal fetuses, using cine phase-contrast MRI. Oxygen saturation (SaO2 ) was measured in the major vessels of 57 fetuses with CHD and 40 controls. RESULTS: Compared with controls, we found lower combined ventricular output in fetuses with single-ventricle physiology, with the lowest being observed in fetuses with severe forms of Ebstein's anomaly. Obstructive lesions of the left or right heart were associated with increased flow across the contralateral side. Pulmonary blood flow was reduced in fetuses with Ebstein's anomaly, while those with Ebstein's anomaly and tricuspid atresia had reduced umbilical flow. Flow in the superior vena cava was elevated in fetuses with transposition of the great arteries, normal in fetuses with hypoplastic left heart, tetralogy of Fallot or tricuspid atresia and reduced in fetuses with Ebstein's anomaly. Umbilical vein SaO2 was reduced in fetuses with hypoplastic left heart or tetralogy of Fallot. Ascending aorta and superior vena cava SaO2 were reduced in nearly all CHD subtypes. CONCLUSIONS: Fetuses with cyanotic CHD exhibit profound changes in the distribution of blood flow and oxygen transport, which result in changes in cerebral, pulmonary and placental blood flow and oxygenation. These alterations of fetal circulatory physiology may influence the neonatal course and help account for abnormalities of prenatal growth and development that have been described in newborns with cyanotic CHD. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Sentinel approach to detect emerging causes of work-related respiratory diseases.

BACKGROUND: The world of work is continually changing, and this could result in new and emerging risks being introduced, including those that may cause work-related respiratory diseases (WRRD). AIMS: To describe recently emerging and new cases of WRRD and the relevant methodology using data in a national occupational respiratory disease surveillance scheme in the UK. METHODS: Incident cases of respiratory diseases reported by physicians to the Surveillance of Work-related and Occupational Respiratory Disease (SWORD) between January 2015 and December 2017 were included. Potentially emerging respiratory hazards manifesting in SWORD data were identified with the following hierarchical approach: (i) new respiratory disease not previously associated with work, (ii) specific exposure/agent not previously associated with WRRD and (iii) industry and/or occupation not previously associated with WRRD. RESULTS: A total of 1215 cases of WRRD were reported to SWORD between January 2015 and December 2017. No new WRRD were identified. Thirteen potentially emerging causes of occupational asthma were identified, including exposures to agents such as ninhydrin. Four potential new causes were identified for interstitial pneumonia, which included wood and brass dust. Two potentially emerging causes of WRRD were identified for inhalational accidents (green coffee and nitrocellulose), hypersensitivity pneumonitis (diphenylmethane diisocyanate and salami mould), rhinitis (morphine and Amaranthus quitensis) and sarcoidosis (prions and horses). CONCLUSIONS: Continuous monitoring and reporting of any new work-related disease is a critical function of any occupational disease reporting scheme. Potential emerging causes of work-related health risks have been identified by using a simple and systematic way of detecting emerging causes of WRRDs.

Treatment of fetal circular shunt with non-steroidal anti-inflammatory drugs.

A circular shunt (CS) is a life-threatening condition involving massive shunting of systemic arterial blood via the ductus arteriosus to the left ventricle without traversing the lungs. In the prenatal setting, it occurs mainly in fetuses with severe forms of Ebstein's anomaly (EA) owing to unrestricted ductal flow and significant pulmonary and tricuspid regurgitation. We aimed to improve the fetal hemodynamics and chances of survival of affected fetuses by inducing ductal constriction using transplacental non-steroidal anti-inflammatory drugs (NSAIDs). Following initiation of treatment between 26 and 34 weeks' gestation, three (75%) of four fetuses with EA/CS responded with sustained ductal constriction and improved hemodynamic function, which allowed continuation of pregnancy for 3-7 weeks and elective delivery. All successfully treated cases underwent neonatal surgery immediately after birth to eliminate the CS and survived. This included two neonates that underwent single-ventricle palliation surgery that required postoperative extracorporeal membrane oxygenation and hemofiltration for transient respiratory and renal failure. The one case that did not respond to treatment with NSAIDs was delivered prematurely for progressive fetal compromise and died shortly after birth. Transplacental treatment with NSAIDs represents a novel approach to controlling fetal CS, avoiding in-utero death and prolonging the pregnancy to a more advanced gestational age, thereby potentially increasing the chances of neonatal survival. This treatment should be considered and initiated at an early stage of systemic steal to prevent brain injury due to hypoperfusion. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Occupational asthma caused by an epoxy amine hardener.

We describe a 43-year-old epoxy floor layer who developed work-related asthma while exposed to an epoxy hardener based on isophorone diamine (IPDA). Challenge exposures to the curing of the epoxy resin system and subsequently to the polyfunctional amine hardener containing IPDA both elicited delayed asthmatic reactions. This report further indicates that exposure to epoxy hardeners containing polyfunctional amines should be considered as a potential cause of occupational asthma. Appropriate work hygiene measures should be implemented to minimize airborne exposure to these volatile compounds.

Chemical determinants of occupational hypersensitivity pneumonitis.

BACKGROUND: Workplace inhalational exposures to low molecular weight (LMW) chemicals cause hypersensitivity pneumonitis (HP) as well as the more common manifestation of respiratory hypersensitivity, occupational asthma (OA). AIMS: To explore whether chemical causation of HP is associated with different structural and physico-chemical determinants from OA. METHODS: Chemical causes of human cases of HP and OA were identified from searches of peer-reviewed literature up to the end of 2011. Each chemical was categorized according to whether or not it had been the attributed cause of at least one case of HP. The predicted asthma hazard was determined for each chemical using a previously developed quantitative structure-activity relationship (QSAR) model. The chemicals in both sets were independently and 'blindly' analysed by an expert in mech anistic chemistry for a qualitative prediction of protein cross-linking potential and determination of lipophilicity (log K ow). RESULTS: Ten HP-causing chemicals were identified and had a higher median QSAR predicted asthma hazard than the control group of 101 OA-causing chemicals (P < 0.01). Nine of 10 HP-causing chemicals were predicted to be protein cross-linkers compared with 24/92 controls (P < 0.001). The distributions of log K ow indicated higher values for the HP list (median 3.47) compared with controls (median 0.81) (P < 0.05). CONCLUSIONS: These findings suggest that chemicals capable of causing HP tend to have higher predicted asthma hazard, are more lipophilic and are more likely to be protein cross-linkers than those causing OA.

Occupational asthma from tafenoquine in the pharmaceutical industry: implications for QSAR.

We report occupational asthma and rhinitis in a formulation pharmacist, employed in the development of tafenoquine. Tafenoquine is a new anti-malarial drug in development; the pure drug substance has an asthma hazard index of zero and previously was not known to be a respiratory sensitizing agent. The implications of this finding for the refinement of quantitative structural analysis of asthmagenic chemicals are discussed.

A refined QSAR model for prediction of chemical asthma hazard.

BACKGROUND: A previously developed quantitative structure-activity relationship (QSAR) model has been extern ally validated as a good predictor of chemical asthma hazard (sensitivity: 79-86%, specificity: 93-99%). AIMS: To develop and validate a second version of this model. METHODS: Learning dataset asthmagenic chemicals with molecular weight (MW) <1 kDa were identified from reports published in the peer-reviewed literature before the end of 2012. Control chemicals for which no reported case(s) of occupational asthma had been identified were selected at random from UK and US occupational exposure limit tables. MW banding was used in an attempt to categorically match the control group for MW distribution of the asthmagens. About 10% of chemicals in each MW category were excluded for use as an external validation set. An independent researcher utilized a logistic regression approach to compare the molecular descriptors present in asthmagens and controls. The resulting equation generated a hazard index (HI), with a value between zero and one, as an estimate of the probability that the chemical had asthmagenic potential. The HI was determined for each compound in the external validation set. RESULTS: The model development sets comprised 99 chemical asthmagens and 204 controls. The external validation showed that using a cut-point HI of 0.39, 9/10 asthmagenic (sensitivity: 90%) and 23/24 non-asthmagenic (specificity: 96%) compounds were correctly predicted. The new QSAR model showed a better receiver operating characteristic plot than the original. CONCLUSIONS: QSAR refinement by iteration has resulted in an improved model for the prediction of chemical asthma hazard.

Development of mechanism-based structural alerts for respiratory sensitization hazard identification.

This study outlines how mechanistic organic chemistry related to covalent bond formation can be used to rationalize the ability of low molecular weight chemicals to cause respiratory sensitization. The results of an analysis of 104 chemicals which have been reported to cause respiratory sensitization in humans showed that most of the sensitizing chemicals could be distinguished from 82 control chemicals for which no clinical reports of respiratory sensitization exist. This study resulted in the development of a set of mechanism-based structural alerts for chemicals with the potential to cause respiratory sensitization. Their potential for use in a predictive algorithm for this purpose alongside an externally validated quantitative structure-activity relationship model is discussed.

Coronary heart disease mortality in treated familial hypercholesterolaemia: Update of the UK Simon Broome FH register.

BACKGROUND AND AIMS: Patients with familial hypercholesterolaemia (FH) have an elevated risk of coronary heart disease (CHD). Here we compare changes in CHD mortality in patients with heterozygous (FH) pre 1992, before lipid-lowering therapy with statins was used routinely, and in the periods 1992-2008 and 2008-2016. METHODS: 1903 Definite (DFH) and 1650 Possible (PFH) patients (51% women) aged 20-79 years, recruited from 21 lipid clinics in the United Kingdom and followed prospectively between 1980 and 2016 for 67,060 person-years. The CHD standardised mortality ratio (SMR) compared to the population in England and Wales was calculated (with 95% Confidence intervals). RESULTS: There were 585 deaths, including 252 from CHD. Overall, the observed 2.4-fold excess coronary mortality for treated DFH post-1991 was significantly higher than the 1.78 excess for PFH (35% 95% CI 3%-76%). In patients with DFH and established coronary disease, there was a significant excess coronary mortality in all time periods, but in men it was reduced from a 4.83-fold excess (2.32-8.89) pre-1992 to 4.66 (3.46-6.14) in 1992-2008 and 2.51 (1.01-5.17) post-2008, while in women the corresponding values were 7.23 (2.65-15.73), 4.42 (2.70-6.82) and 6.34 (2.06-14.81). Primary prevention in men with DFH resulted in a progressive reduction in coronary mortality over the three time-periods, with no excess mortality evident post-2008 (0.89 (0.29-2.08)), although in women the excess persisted (post-2008 3.65 (1.75-6.72)). CONCLUSIONS: The results confirm the benefit of statin treatment in reducing CHD mortality, but suggest that FH patients with pre-existing CHD and women with FH may not be treated adequately.

Relationship between apolipoprotein(a) phenotype, lipoprotein(a) concentration in plasma, and low density lipoprotein receptor function in a large kindred with familial hypercholesterolemia due to the pro664----leu mutation in the LDL receptor gene.

In a large kindred of 66 individuals, 22 were identified as heterozygous and 3 as homozygous for a mutation (pro664----leu) in the LDL-receptor gene that gives rise to familial hypercholesterolaemia (FH). All the heterozygotes had a raised level of plasma total cholesterol and low density lipoprotein cholesterol, but were remarkably free from premature coronary disease. Determination of apolipoprotein(a) (apo(a)) phenotype and lipoprotein(a) (Lp(a)) concentration in plasma revealed that in many instances, involving individuals with various apo(a) phenotypes, there was no difference in plasma Lp(a) concentration between an FH heterozygote and an unaffected sibling with the same apo(a) phenotype. No significant difference in Lp(a) concentration was observed between groups of FH and non-FH of the same apo(a) phenotype, although in each case the mean value for the FH group was greater than that for the non-FH group. There was also evidence for an inherited trait that markedly increased Lp(a) concentration, which did not segregate with apo(a) phenotype or the defective LDL-receptor allele. The data provide no evidence for a strong multiplicative interaction between the gene loci for apo(a) and the LDL receptor.

Genetic causes of familial hypercholesterolaemia in patients in the UK: relation to plasma lipid levels and coronary heart disease risk.

AIMS: To determine the relative frequency of mutations in three different genes (low-density lipoprotein receptor (LDLR), APOB, PCSK9), and to examine their effect in development of coronary heart disease (CHD) in patients with clinically defined definite familial hypercholesterolaemia in UK. PATIENTS AND METHODS: 409 patients with familial hypercholesterolaemia patients (158 with CHD) were studied. The LDLR was partially screened by single-strand conformational polymorphism (SSCP) (exons 3, 4, 6-10 and 14) and by using a commercial kit for gross deletions or rearrangements. APOB (p.R3500Q) and PCSK9 (p.D374Y) were detected by specific assays. Coding exons of PCSK9 were screened by SSCP. RESULTS: Mutations were detected in 253 (61.9%) PATIENTS: 236 (57.7%) carried LDLR, 10 (2.4%) carried APOB p.Q3500 and 7 (1.7%) PCSK9 p.Y374. No additional mutations were identified in PCSK9. After adjusting for age, sex, smoking and systolic blood pressure, compared to those with no detectable mutation, the odds ratio of having CHD in those with an LDLR mutation was 1.84 (95% CI 1.10 to 3.06), for APOB 3.40 (0.71 to 16.36), and for PCSK9 19.96 (1.88 to 211.5; p = 0.001 overall). The high risk in patients carrying LDLR and PCSK9 p.Y374 was partly explained by their higher pretreatment cholesterol levels (LDLR, PCSK9 and no mutation, 10.29 (1.85), 13.12 and 9.85 (1.90) mmol/l, respectively, p = 0.001). The post-statin treatment lipid profile in PCSK9 p.Y374 carriers was worse than in patients with no identified mutation (LDL-C, 6.77 (1.82) mmol/l v 4.19 (1.26) mmol/l, p = 0.001, HDL-C 1.09 (0.27) mmol/l v 1.36 (0.36) mmol/l, p = 0.03). CONCLUSIONS: The higher CHD risk in patients carrying PCSK9 p.Y347 or a detected LDLR mutation supports the usefulness of DNA testing in the diagnosis and management of patients with familial hypercholesterolaemia. Mutations in PCSK9 appear uncommon in patients with familial hypercholesterolaemia in UK.

Magnetic resonance imaging reveals elevated aortic pulse wave velocity in obese and overweight adolescents.

The aortic pulse wave velocity (PWV) measured via cardiac magnetic resonance (CMR) can be used to non-invasively assess changes in arterial stiffness and potential underlying vascular dysfunction. This technique could unmask early arterial dysfunction in overweight and obese youth at risk for cardiovascular disease. We sought to determine the association between vascular stiffness, percentage body fat, body mass index (BMI), and cardiac function in adolescents across the weight spectrum through both CMR and standard applanation tonometry (AT)-based PWV measurements. PWV and left-ventricular cardiac function were assessed using 3.0 T CMR in obese and overweight (OB/OW) participants (n = 12) and controls (n = 7). PWV was also estimated via carotid-femoral AT. OB/OW participants did not differ from healthy-weight controls regarding cardiometabolic risk factors or physical activity levels, but there was a trend towards higher levels of triglycerides in obese/overweight participants (P = 0.07). Mean PWV was higher in obese participants when corrected for age and sex (P = 0.01), and was positively associated with BMI (ß = 0.51, P = 0.02). PWV estimated through AT was not significantly different between groups. Cardiac function measured by left-ventricular ejection fraction z-score was inversely associated with mean PWV (ß = -0.57, P = 0.026). Increasing arterial stiffness and decreasing cardiac function were evident among our overweight and obese cohort. PWV estimated by CMR could detect early increases in arterial stiffness vs. traditional AT measurements of PWV.

The inhibition of colon-26 adenocarcinoma development and angiogenesis by topical diclofenac in 2.5% hyaluronan.

Topical diclofenac in 2.5% hyaluronan inhibits basal cell carcinoma, actinic keratosis, and murine colon-26 growth in vivo. colon-26 tumor growth was preceded by angiogenesis and reduced apoptotic and mitotic indices. Diclofenac reduced proliferation and viability in vitro, and stimulated apoptosis. Hyaluronan inhibited proliferation and viability at 1 mg/ml but was inactive below this level. Topical application of diclofenac inhibited tumor prostaglandin synthesis and retarded angiogenesis and tumor growth (ratio of treatment:control, 0.174). The mitotic index remained unaltered in vivo, whereas the apoptotic index and necrosis were increased. Topical vehicle exhibited slight antitumor and antiangiogenesis activity. The substantial quantities of diclofenac delivered locally in hyaluronan may exhibit antitumor activity in similar fashion to those seen in vitro and explain its clinical efficacy.

Risk factors for cardiovascular disease in IDDM. A study of identical twins.

Patients with insulin-dependent diabetes mellitus (IDDM) have an excess mortality, predominantly attributable to cardiovascular disease. To determine the effect of IDDM on potential risk factors for cardiovascular mortality, we studied subjects from the British Diabetic Twin Study Group. Forty-five identical twin pairs discordant for IDDM were recruited in addition to 45 matched nondiabetic singleton control subjects. All were selected to be normotensive and to have normal albumin excretion rates. Four variables differed significantly between the diabetic twins and their nondiabetic identical co-twins: diabetic twins had higher systolic blood pressure (sBP) ([mean +/- SD] 127 +/- 17 vs. 123 +/- 18 mmHg, P < 0.05), high-density lipoprotein (HDL) cholesterol (1.36 +/- 0.31 vs. 1.25 +/- 0.29 mM, P < 0.05) and fibrinogen (3.23 +/- 0.81 vs. 2.98 +/- 0.71 mg/ml, P < 0.05) but lower factor VII (114 +/- 34 vs. 122 +/- 31%, P < 0.05). All four of these risk factors were significantly correlated (P < 0.001) within the identical twin pairs, as were the other risk factors. These significant correlations within twins for the risk factors studied reflects the impact of shared genetic and environmental influences. IDDM affects sBP, HDL cholesterol, fibrinogen, and factor VII, but only sBP and fibrinogen are affected adversely.

Relationship between chemical structure and the occupational asthma hazard of low molecular weight organic compounds.

AIMS: To investigate quantitatively, relationships between chemical structure and reported occupational asthma hazard for low molecular weight (LMW) organic compounds; to develop and validate a model linking asthma hazard with chemical substructure; and to generate mechanistic hypotheses that might explain the relationships. METHODS: A learning dataset used 78 LMW chemical asthmagens reported in the literature before 1995, and 301 control compounds with recognised occupational exposures and hazards other than respiratory sensitisation. The chemical structures of the asthmagens and control compounds were characterised by the presence of chemical substructure fragments. Odds ratios were calculated for these fragments to determine which were associated with a likelihood of being reported as an occupational asthmagen. Logistic regression modelling was used to identify the independent contribution of these substructures. A post-1995 set of 21 asthmagens and 77 controls were selected to externally validate the model. RESULTS: Nitrogen or oxygen containing functional groups such as isocyanate, amine, acid anhydride, and carbonyl were associated with an occupational asthma hazard, particularly when the functional group was present twice or more in the same molecule. A logistic regression model using only statistically significant independent variables for occupational asthma hazard correctly assigned 90% of the model development set. The external validation showed a sensitivity of 86% and specificity of 99%. CONCLUSIONS: Although a wide variety of chemical structures are associated with occupational asthma, bifunctional reactivity is strongly associated with occupational asthma hazard across a range of chemical substructures. This suggests that chemical cross-linking is an important molecular mechanism leading to the development of occupational asthma. The logistic regression model is freely available on the internet and may offer a useful but inexpensive adjunct to the prediction of occupational asthma hazard.