Exhaled nitric oxide and clinical phenotypes of childhood asthma

Respiratory Research

Table 2 Orthogonal varimax rotation results

28 variables	factors
	1	2	3	4	5	6	7	8	9
Clinical
gender								- 0.765
age		- 0.879
height		- 0.889
weight		- 0.905
BMI		- 0.751
early wheezing (< 2 years)					- 0.339		0.565		- 0.368
atopy (positive SPT)					0.800
parental smoking									0.764
Treatment
LABA			0.840
ICS treatment			0.872
ICS dose			0.898
ICS dose > 200 μg/d			0.814
Clinical events
partially or uncontrolled				0.439			0.626
days with symptoms				0.089			0.777
exacerbation				0.942			0.054
days with oral steroid				0.940			0.085
Baseline PFT values
FEV₁						0.843
FEV1/FVC	0.843
sRaw	- 0.609
RV/TLC		0.645				0.454
FEF_50%/TLC	0.834							- 0.050
Post bronchodilator PFT values
FEV₁						0.885
FEV1/FVC	0.757
sRaw	- 0.391
RV/TLC		0.664
FEF_50%/TLC	0.797							0.286
FEV₁ response to BD %	- 0.569				0.397			0.392
Exhaled NO	- 0.061	- 0.132	- 0.119	- 0.059	0.789	- 0.149	0.064	0.030	0.076

PFT: denotes pulmonary function tests
All results for exhaled NO are shown in italic for information.
Factor analysis (PCA in our study) is based on the procedure for obtaining a new set of uncorrelated (orthogonal) variables, usually fewer in number than the original set (9 instead of 28 in our study), that reproduces the co-variability observed among a set or original variables. Then we requested a rotation of the resulting factors which follows completion of the analysis of the data. The most common rotation performed is the Varimax rotation[23]. This tends to produce "simple structure", that is, factors which have very high (that are provided in the table) or very low (provided for exhaled NO) loadings for the original variables and thus simplifies the interpretation of the resulting factors.

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