This study investigated the clinical course of gouty arthritis that might cause sudden incapacitation of the cockpit personnel in flight. Twelve persons with the history of gouty arthritis were chosen as the gouty arthritis group (G-group) from a total number of 4,075 male crew members who underwent aviation medical examination (AME) between April,1993 and March,1994. Age of gouty arthritis, obesity, fluctuation of serum uric acid (SUA) level, type and duration of hyperuricemia (SUA: over 8.0mg/dl) and renal function were investigated. To investigate differences in these variables between the G-group and the asymptomatic hyperuricemia group (A-group), another 12persons who showed asymptomatic hyperuricemia without gouty arthritis were chosen as an age and duration of hyperuricemia matched sample. The results were as follows; 1) The G-group consisted of 12 persons and comprised 0.29% of active flight crews. Mean age at the first episode of gouty arthritis was 45.2±6.8 (36∼56) years old and the mean duration from the onset of hyperuricemia to the first appearance of gouty arthritis was 4.6±2.1 (1.0∼7.8) years. 2) There were no significant differences in blood pressure, obesity, complications, CCr, or CUA between the two groups. Fifty percent of the G-group and 41.7% of the A-group were underexcreters of uric acid. 3) With regard to the SUA (mg/dl) level on the AME, there was no significant difference in either the full average of SUA (G-group 7.7±0.5: A-group 7.5±0.2) or the partial average of SUA (G-group 7.8±0.6: A-group 7.8±0.3) after the onset of hyperuricemia between the two groups. Average SUA level just before the episode of gouty arthritis in the G-group was significantly higher than that at the last observation point in the A-group. The appearance rate of hyperuricemia in the G-group was significantly higher than that in the A-group. 4) Although there were no significant differences for average of SUA MAX in each group, average of SUA MIN in the G-group was lower and ΔSUA (fluctuation of SUA level) in the G-group was higher than that of the A-group (2.5±0.9mg/dl VS.1.8±0.6mg/dl respectively, p<0.05). 5) By administration of allopurinol (100∼200mg/day), the level of SUA decreased from 8.4±0.8mg /dl to 6.0±1.2mg/dl, however Ccr and CUA showed no significant change in the G-group. These results suggested that fluctuation of SUA levels and the appearance rate of hyperuricemia on the AME had a greater influence upon the occurrence of gouty arthritis than the average levels of SUA in flight crews.
We investigated circadian changes in urine pH in 157 gouty patients. The urine pH of each patients was measured 3 times a day for 2 weeks: the first urine specimen immediately after rising, and diurnal and nocturnal urine specimens, regard of meal times. All patients were divided into the following four groups according to the pH of the morning urine specimen and subsequent changes: Type aA: pH<5.8 throughout the day. Type bB: pH>5.8 throughout the day. Type aB: pH<5.8 only in the morning urine. Type C: pH varied irregularly or patient did not belong to any of the above 3 groups. Type aA was found in 39% of 157 patients, type bB in 24%, type aB in 13% and type C in 24%. To evaluate the role of acidic urine in gouty patients, we compared some laboratory data between the aA type and the bB type. The serum uric acid value in the aA type was significantly higher than that in the bB type (p<0.005). The incidence of abnormal value of creatinine clearance and serum creatinine levels were higher in the aA type than in the bB type (p>0.05). The incidence of complicated urolithiasis was also higher in the aA type than in the bB type (p>0.05). These data imply that gouty patients with acidic urine have more severe stage than those without acidic urine. Determination of the presence or absence of acidic urine has commonly been based on the pH of morning urine, but determination should be based on the circadian changes in urine pH. In this paper, we propose a simple method for classifying urinary pH type. This method seemed to be useful for assessing acidic urine and will also facilitate the alkalization of urine in gouty patients.