Chlamydia pneumoniae infection and ethnic origin

ABSTRACT

OBJECTIVES: To test the association of Chlamydia pneumoniae infection with ethnic origin. DESIGN: A prospective study by micro-immunofluorescence of antibodies to C. pnuemoniae in patients admitted to one hospital with a variety of non-pulmonary, non-cardiovascular disorders. SETTING: A large district general hospital serving a multi-ethnic inner-city population in Birmingham, UK. SUBJECTS: There were 1518 patients, 1061 of whom were Caucasian, 290 Asian and 167 Afro-Caribbean. Each of 169 Asian and 141 Afro-Caribbeans was matched with two Caucasians for age, sex, smoking habit, steriod medication and date of admission, and logistic regression methods were used to compared the effects on C. pneumoniae antibody levels of ethnic origin, these confounding variables, diabetes mellitus and social deprivation. OUTCOME MEASURES: Serological evidence of acute C. pnuemoniae infection or reinfection (defined by titres of IgM > or = 8, a four-fold rise in IgG or IgG > or = 512) and previous infection (IgG 64-256 or IgA > or = 8). RESULTS: Results showed 4.8 percent of Caucasians, 6.6 percent of Asians and 10.2 percent of Afro-Caribbeans had antibody titres suggesting acute (re) infection; and 11.2 percent of Caucasians, 13.4 percent Asians and 21.0 percent of Afro-Caribbeans had titres suggesting previous infection. On chi 2 analysis, the distributions of the three possible serological outcomes (acute, previous and no infection) differed significantly (p < 0.05) between the Afro-Caribbean and Caucasian groups, but not between Asians and Caucasians or between Afro-Caribbeans and Asians. After adjusting for possible confounding variables, odds ratios for Afro-Caribbean versus Caucasian origin were 5.5 (95 percent confidence intervals 2.0-15.0) for acute (re) infection and 1.9 (1.0-3.7) for previous infection. CONCLUSION: Our results suggest that C. pneumoniae infection may be more prevalent among Afro-Caribbean than among Caucasian people, and that Asians may lie somewhere them in this respect. The behaviour of this pathogen in different ethnic groups deserve further investigation. Future studies of this organism should give due attention to the ethnic origins of patients.(AU)