Results
The study population included 123 children (5-18 years) of which 64
(52%) were male. The MCC was positive in 81 (65.9%) children
indicating the presence of AHR. In Table 1, the characteristics of the
study population are summarized according to the presence of AHR. The
median age of children with AHR was significantly younger at the time of
diagnosis compared to those without AHR (9.7 vs 12.3 years; P = .001).
The prevalence of aeroallergen sensitization in the skin prick test was
significantly higher in children with AHR when compared to those without
AHR (35.7% vs 58.0%; P = .019). Subclassification according to
individual allergen groups revealed for AHR positive children an
elevated incidence of allergy to tree pollen (11.9% vs 37.0%; P =
.003), animal dander (9.5% vs 27.2%; P = .023) and house dust allergy
(21.4% vs 44.4%; P = .012). With regard to admission symptoms,nocturnal cough (9.5% vs 30.9%; P = .008), wheezing not
associated with colds (4.8% vs 22.2%; P = .013) and wheezing
associated with colds (35.7% vs 58.0%; P = .019) were observed
significantly more frequently in AHR positive children compared to
children without AHR. Combining wheezing symptoms (ever wheezing )
resulted in an improved significance (40.5% vs 66.7%; P = .005), while
significance was reduced for combinations of nocturnal cough withexercise-induced cough . However, dyspnea andexercise-induced dyspnea , even in combination with other
parameters, did not reach significance. For the spirometry items, only a
baseline forced expiratory flow at 75% of vital capacity
(FEF75) <65% was found significantly more
frequently in AHR positive children compared to the group without AHR
(14.3% vs 30.9%; P = .045). The diagnostic value of significant
parameters in the univariate analysis is shown in Table 2.
A comparison of laboratory parameters reveals that the percentage of
children with a blood eosinophilia count over 500/ μL was significantly
elevated in the AHR positive group compared with children without AHR
(22.8% vs 2.4%; P = .002; N = 80). Also, the median of the percentage
of blood eosinophilia was significantly higher in AHR positive children
compared with the group without AHR (5.6% vs 2.8%; P = .004; N = 93).
Multivariate logistic regression including age, ever wheezing ,nocturnal cough , tree pollen allergy and
FEF75<65% confirmed that all parameters
chosen are independent predictors of the occurrence of AHR. In Table 3,
the results of multivariate analysis are summarized. Multivariate
prediction score values, weighted as described in the methods section,
were calculated for each child as follows: individual score value = 14 x
tree pollen allergy (yes = 1, no = 0) + 11 x ever wheezing (yes = 1, no
= 0) + 13 x nocturnal cough (yes = 1, no = 0) + 11 x
FEF75<65% (yes = 1, no = 0) – 2 x age (5 –
18 years) + 36. The last summand was added to get only positive score
values ranging from 0 to 75 points. The individual score values
calculated for our patients ranged from 3 to 61 with a median
(interquartile range) of 32 (19-41). The risk of the occurrence of AHR
increased with the score value. In Table 4, the test characteristics of
the multivariate score at various cutoff points are summarized. At a
cutoff point of 35 the presence of AHR is predicted with a specificity
of 90.5% and a PPV of 91.5%. The ROC curve displaying sensitivity and
specificity of score with ascending cutoff points is shown in Figure 2.
The area under the curve (AUC) was 0.813.