Roelants14OCT2004

Screening for asthma: identifying asthmatic children in the absence of a gold standard: 

Screening for asthma: identifying asthmatic children in the absence of a gold standard Mathieu Roelants & Karel Hoppenbrouwers M. Roelants, K. Hoppenbrouwers, M. Daelemans, P. Vermeire, F. De Baets, A. Aerts, F. Govaerts, O. Moens, E. Colen, C. Glorieux, B. Aggoune, R. Van den Broeck, E. De Boever, Jeugdgezondheidszorg, Katholieke Universiteit Leuven

INTRODUCTION - ASTHMA: 

INTRODUCTION - ASTHMA Most common chronic disease in childhood High prevalence, and rising Often not recognized 2 potential screening instruments: ISAAC/FRAST No gold standard

ASTHMA – DEFINITION: 

ASTHMA – DEFINITION Asthma causes recurring episodes of wheezing, breathlessness, chest tightness, and coughing particularly at night or in the early morning. Asthma is a chronic inflammatory disorder of the airways. Chronically inflamed airways are hyperresponsive; they become obstructed and airflow is limited (by bronchoconstriction, mucus plugs, and increased inflammation) when airways are exposed to various risk factors. (NHLBI, NIH, US)

ASTHMA – DEFINITION: 

ASTHMA – DEFINITION Asthma causes recurring episodes of wheezing, breathlessness, chest tightness, and coughing particularly at night or in the early morning.  anamnesis, interview, questionnaire (ISAAC ) Asthma is a chronic inflammatory disorder of the airways. Chronically inflamed airways are hyperresponsive; they become obstructed and airflow is limited (by bronchoconstriction, mucus plugs, and increased inflammation) when airways are exposed to various risk factors.  Challenge test (histamine/metacholine, exercise) (NHLBI, NIH, US)

ISAACInternational Study of Asthma and Allergies in Childhood: 

ISAAC International Study of Asthma and Allergies in Childhood 1. Has your child ever had wheezing or whistling in the chest at any time in the past? 2. Has your child had wheezing or whistling in the chest in the last 12 months? 3. How many attacks of wheezing has your child had in the last 12 months? 4. In the last 12 months, how often, on average, has your child's sleep been disturbed due to wheezing? 5. In the last 12 months, has wheezing ever been severe enough to limit your child's speech to only one or two words at a time between breaths? 6. Has your child ever had asthma? 7. In the last 12 months, has your child's chest sounded wheezy during or after exercise? 8. In the last 12 months, has your child had a dry cough at night, apart from a cough associated with a cold or chest infection? 9. Has your child had asthma in the last 12 months? [NON ISAAC] 10. In the last 12 months, did your child use any medication against asthma? [NON ISAAC] 11. Please specify medication: …….. [NON ISAAC]

FRASTfree running asthma screening test: 

FRAST free running asthma screening test = induce pulmonary reaction through exercise

STUDY PLAN: 

STUDY PLAN Screening phase ± 6000 pupils, first year primary school Informed consent Socio-demographic questionnaire ISAAC, FRAST (PEF) Validation phase random selection of 4 x 100 pupils Interview at home (child + parents) by medical doctor Skin prick (allergy) tests Evaluation by expert panel

STUDY PLAN: 

STUDY PLAN validation screening

RESULTS: ISAAC: 

RESULTS: ISAAC Completed for 5483 pupils 307 (5.6%) known asthma 286 (93.8%) with positive test 33.9% severe asthma 5176 (94.4%) no known asthma 1136 (22.0%) with positive test 1.3% severe asthma

RESULTS: ISAAC: 

RESULTS: ISAAC

RESULTS: FRAST: 

RESULTS: FRAST Completed by 5146 pupils Positive test (PEF reduction  15%) in 574 pupils (11.2%) 18.6% of known asthmatics 10.7% of other pupils

RESULTS: FRAST: 

RESULTS: FRAST

RESULTS: ISAAC & FRAST (combined): 

RESULTS: ISAAC & FRAST (combined) Pupils w/o known asthma FRAST ISAAC positive negative positive 139 (13.4) 898 (86.6) 1037 (27.0) (2.9) (20.9) (18.6) (21.5) negative 375 (9.9) 3405 (90.1) 3780 (73.0) (7.8) (79.1) (70.7) (78.5) 514 (10.7) 4303 (89.3) 4817

RESULTS: ISAAC & FRAST (combined): 

RESULTS: ISAAC & FRAST (combined) asthma EIB

SUMMARY OF SCREENING PHASE: 

SUMMARY OF SCREENING PHASE

VALIDATION PHASE: 

VALIDATION PHASE Random sample from screened pupils Standardized interview by medical doctor at home Skin prick tests Expert (pediatric lung specialists) decision: I- F- I- F+ I+ F- I+ F+ asthma screened: 3405 375 898 139 280 validated: 92 91 78 70 48 Negative 78 (84.8) 71 (78.0) 47 (60.3) 30 (42.9) 5 (10.4) undecided 0 (0.0) 1 (1.1) 2 (2.6) 1 (1.4) 2 (4.2) Positive 14 (15.2) 19 (20.9) 29 (37.2) 39 (55.7) 41 (85.4)

DIAGNOSTIC PROPERTIES: 

DIAGNOSTIC PROPERTIES ISAAC or FRAST ISAAC FRAST ISAAC and FRAST Sensitivity 48.9 41.1 15.6 7.8 Specificity 75.9 83.7 90.6 98.4 PPV 35.1 40.2 30.7 56.5 NPV 84.8 84.2 80.1 80.0 Efficiency 70.2 74.7 69.4 79.3 PLR 2.0 2.5 1.6 4.8 NLR 0.7 0.7 0.9 0.9 prevalence of “unknown asthma” in the population: 19.9 % (16.4 – 28.2%) total asthma prevalence: 24.8 % (19.6 – 30.1%)

SUMMARY & CONCLUSIONS: 

SUMMARY & CONCLUSIONS Prevalence of symptoms as expected, but validation is less favourable than reported in literature No test (combination) is sufficiently specific for routine screening Pupils with positive ISAAC and FRAST tests closely resemble known asthmatics High prevalence of asthma (known or unknown) warrants further action