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Cluster Phenotypes - Background Phenotypes such as “asthma” are difficult to define, variable over time and/or are subject to recall bias and are “syndromic”. Subtypes of asthma are known to exist - –Eosinophilic, neutrophilic, paucigranulocytic, atopic, occupational. There are intermediate phenotypes – –IgE, atopy, AHR, FEV1, eNO Phenotypes do not “capture” “asthma” Ho: Clusters will capture phenotypes that more strongly associate with genetic variation than “asthma”
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Cluster Phenotypes Cluster Analysis (SAS) Busselton Health Survey 2005-7 All adults with: –Age, Sex, FEV1, FVC, eNO, eosinophil count, BMI, airway hyper-responsiveness (AHR), atopy (skin tests) n = 1,970 7 clusters (each with n > 100)
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Cluster Phenotypes Cluster n Doctor-diagnosed Hay Fever (%) Doctor-diagnosed Asthma (%) 1 106 52.831.1 2 226 28.817.7 3 215 45.640.0 4 391 42.218.2 5 127 31.524.4 6 441 31.115.6 7 464 20.25.4
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Cluster Phenotypes Cluster n Cluster Variables Outcome Variables “Descriptors” 1 106 High eNO, high eosinophils, low BHR, high atopy Smoke low, HF high, asthma Allergic sneezing, wheezing twitchers 2 226 Females, obese, no AHR, low atopyFat Freewheelers 3 215 Reduced lung function, all AHR, moderate atopy High asthmaChronic wheezers 4 391 Males, no AHR, very atopicHFBlotchy blokes 5 127 Males, poor lung function, no AHRSmoke highPuffing Old Blokes 6 441 Younger females, no AHR, low eNO, low eosinophils, low atopy Smoke low, asthma low Sanctimonious shielas 7 464 Older, good lung function, no AHR, low atopy Smoke low, HF low, asthma very low Survivors
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Cluster Phenotypes - Questions How many clusters? –? Sub-clusters What other variables to collect? Include exposure? Include questionnaire data? Include treatment? Do clusters suggest pathways? Best gene association strategy –GWAS, candidate (from lit. or pathways)?
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Cluster Phenotypes ClusternAge Sex (%F) FEVPPRFEVFVCeNOEOSINBMIAHRATOPY 110649.241.597.776.960.05.825.719.881.1 222653.978.392.880.916.13.234.50.030.5 321553.356.788.274.023.63.926.9100.071.2 439151.616.997.377.820.74.127.30.095.4 512769.424.468.458.320.43.826.40.149.6 644138.780.8100.981.714.62.724.00.045.1 746468.243.3104.077.018.33.026.20.05.2
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Excessive Airway Narrowing in a General Population n = 201 James et al. ARRD 1992;146:895-9
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Airway Compartments Lumen area Smooth muscle Inner wall area Outer wall area Basement membrane perimeter
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Excessive Airway Narrowing
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Airway smooth muscle in asthma: collaborative study James et al AJRCCM (rejected), Thorax (rejected), ERJ (submitted)
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Decline in lung function - the Busselton Health Study Females James et al AJRCCM 2005;171:109
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Sears M et al. N Engl J Med 2003;349:1414-1422 FEV1/FVC Mean (SE) from 9-26 Yrs in Males and Females, by Pattern of Wheezing A Longitudinal Study of Childhood Asthma Followed to Adulthood
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Asthma (ever) (p <0.001)* *1981 vs 2005/07 Q. “Have you ever had asthma?” Q. “Has a doctor ever told you that you had asthma?”
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Current Asthma (AHR + recent wheeze)
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Wheeze (ever) (p <0.001)* (p <0.029)* (p <0.001)* Q. “Has your chest sounded wheezy on most days or nights?” Q. “Has your chest ever made a wheezing or whistling sound ?” *1981 vs 2005/07
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Recent Wheeze Wheeze <12 months
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Shortness of Breath
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Cough/Phlegm (p <0.02)* *1981 vs 2005
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Smoking
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Bronchitis Q. “Have you ever had bronchitis? Q. “Has your doctor ever told that you had bronchitis?”
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