Does rheumatic fever occur usually between the ages of 5 and 15 years?

It has long been considered that rheumatic fever usually occurs in children between the ages of 5 and 15 years. However, supporting data from the developing countries are insufficient. It is important to know the age of occurrence of rheumatic fever for clinical and public health purposes. To describe the age distribution of Bangladeshi subjects, we have reviewed the records of all patients who attended with acute rheumatic fever in the outpatient department of the National Center for Control of Rheumatic Fever and Heart Diseases, Dhaka, during June 1990 through November 1995. During this period 630 subjects were diagnosed to have acute rheumatic fever defined by the revised Jones criteria. Of them, 535 (84.9%) presented with first attack. Their age ranged from 3 to 30 years, and a skewness to the right of the age distribution was observed. Thus, we used percentile distribution to determine reference range of age. The 2.5 and 97.5 percentiles were 5 and 22 years, respectively. Their mean (standard deviation) and median age were 12.7 (4.4) and 12 years, respectively. Slightly more than 22% of subjects were older than 15 while less than 1% were younger than 5 years. This finding was supported by multiethnic data from other developing countries. The current analysis warrants reevaluation of the prevailing conviction for age of occurrence of rheumatic fever. In conclusion, the age reference range for occurrence of rheumatic fever in Bangladesh should be considered to be 5 to 22 years but not 5 to 15 years.

Effects of pulse separation on detection thresholds for electrical stimulation of the human cochlea.

Effects of pulse separation on detection of electrical stimulation of the cochlea were studied in 12 profoundly deaf human subjects with Nucleus 22 cochlear implants. Biphasic symmetric pulses were used. Pulse separation is the time from offset of one biphasic pulse to the onset of the next biphasic pulse in the train. Effects of pulse separation were studied in the context of different covariables in four stages of the experiment. Effects of pulse separation seen in the different stages were similar, despite the different covariables. Both pulse separation and the total number of pulses per stimulus seem to be important variables affecting stimulus detection. For 0.5 ms/phase pulses, thresholds were lowest at the shortest pulse separations tested (0.2-1.1 ms) and increased as a function of pulse separation. For 2 ms/phase pulses, detection thresholds were lowest at pulse separations around 7.5 ms, in most cases, and higher at both longer and shorter pulse separations. These results suggest that interactions among adjacent pulses can either hinder or facilitate detection of the signal depending on the magnitudes of pulse separation and phase duration. Pulse separations at which thresholds measured for 2 ms/phase pulses were minimum were fairly consistent across subjects and did not correlate well with speech recognition scores. However, significant variation in this measure across species has been seen.