DISCRIMINANT-ANALYSIS OF SYMPTOM PATTERN AND SERUM ANTIBODY-TITERS INHUMIDIFIER RELATED DISEASE

Background-The heterogeneous patterns of symptoms among factory worker s exposed to aerosols from contaminated air humidifiers were analysed to assess the association between specific symptoms and the serum IgG antibody response to the humidifier water contaminants, and to test th e ability of specific symptoms to predict this antibody response. Meth ods-Symptoms from 88 factory workers were surveyed by a doctor adminis tered questionnaire and compared with their serum IgG antibody titres to humidifier water contaminants quantified by enzyme immunoassay. Res ults-The strength of association between individual symptoms and antib ody showed that fever, shivering or chills, influenza-like symptoms, o r headache were individually significantly associated with the presenc e and higher titres of antibody. This was also true for those subjects whose symptoms were most pronounced during the first day of the worki ng week. Within each subject's full symptom profile there were signifi cant associations between the description of chest tightness, breathle ssness, and wheeze; between headache and influenza like symptoms; betw een fever and shivering or chills; and between intermittent onset and general tiredness. Discriminant analysis of the full symptom profiles showed that there was maximum information content in five independent parameters, namely, the descriptions of fever, headache, and chest tig htness, the timing of their onset, and the readiness to describe misce llaneous symptoms in addition to those in the questionnaire. On the ba sis of these criteria 72% of subjects could be classified according to their antibody state. Cluster analysis with these five independent pa rameters described four symptom clusters: one associated with high med ian antibody levels, one with low, and two with zero median levels. Th ese were, respectively: (1) fever with headache and chest tightness; ( 2) either no or few symptoms; (3) chest tightness and headache with in termittent onset; (4) headache and miscellaneous symptoms with intermi ttent onset. Conclusions-The association between serum antibody titres and specific symptom patterns may identify different categories of di sease which constitute the spectrum known as humidifier related diseas e, and strengthens the hypothesis that antibody may be involved in the pathogenesis of some components of the disease.