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Selective antibody deficiency and its relation to the IgG2 and IgG3 subclass titers in recurrent respiratory infections.

BACKGROUND
Selective antibody deficiency with normal immunoglobulins (SADNI) may be identified as part of distinct primary or secondary immunodeficiency disorders. The clinical manifestations include recurrent, often severe or prolonged, upper or lower respiratory tract infections.


OBJECTIVES
To evaluate SADNI in patients with recurrent sinopulmonary infections and its relation to IgG subclass deficiencies.


METHODS
In a case-control study, anti-pneumococcal antibody titer and IgG2, IgG3 levels before injection of pneumococcal vaccine and anti-pneumococcal antibody titer at least 4 weeks after vaccination were measured in 46 patients and 54 controls. The results were compared using student's t-test.


RESULTS
There was a significant correlation between age and anti-pneumococcal antibody titers before and after vaccination in patients. No significant relation was found between pre and post vaccination pneumococcal antibody titer and IgG2 and IgG3 in cases and controls (p>0.05). The mean of anti-pneumococcal antibody before and after vaccination were significantly different in cases and controls and were higher in control group (p=0.01, p=0.001, respectively). Anti-pneumococcal antibody titers in 97.8% of cases and 100% of controls group were normal (>3.4 µg/ml). 34.8% of cases and 9.1% of controls had low titers of anti-pneumococcal antibody (<20 µg/ml) while 18.7% of cases and no controls failed to respond to vaccine.


CONCLUSION
Evaluation of anti-pneumococcal antibody titer in patients with recurrent, chronic and severe respiratory infections with normal immunoglobulin levels seems to be necessary as early diagnosis. Treatment of such cases could prevent later sequelae such as mastoiditis and bronchiecstasia.