A formula has been developed to predict creatinine clearance (C_cr) from serum creatinine (S_cr) in adult males: Ccr = (140 – age) (wt kg)/72 × S_cr(mg/100ml) (15% less in females). Derivation included the relationship found between age and 24-hour creatinine excretion/kg in 249 patients aged 18–92. Values for C_cr were predicted by this formula and four other methods and the results compared with the means of two 24-hour C_cr’s measured in 236 patients. The above formula gave a correlation coefficient between predicted and mean measured Ccr·s of 0.83; on average, the difference between predicted and mean measured values was no greater than that between paired clearances. Factors for age and body weight must be included for reasonable prediction.

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Excess beta2-agonist use in asthmatics has been associated with increased mortality and morbidity. The mechanisms responsible for these observations are unknown. We hypothesized that polymorphisms of the beta2-adrenergic receptor (beta2AR) at amino acid positions 16, 27, and 164, which are known to alter receptor functions in vitro, may predispose asthmatics to fatal/near-fatal asthma and/or modify asthma severity. In preliminary studies we found significant differences in allele frequencies due to ethnic background: Caucasian, Black, Asian Gly16 = 0.61, 0.50, 0.40 and Gln27 = 0.57, 0. 73, 0.80, respectively. beta2AR genotyping was performed on DNA from Caucasians classified as nonasthmatic/nonatopic (n = 84), fatal/near-fatal asthmatics (n = 81) and mild/moderate asthmatics (n = 86). No polymorphism or haplotype was found to be associated with fatal/near-fatal asthma. However, the Gly16/Gln27 haplotype, which undergoes enhanced downregulation in vitro, was substantially more prevalent in moderate asthmatics than in mild asthmatics (p = 0.003, odds ratio = 3.1). We conclude that the beta2AR genotype is not a major determinant of fatal or near-fatal asthma. Furthermore, allele frequency variation among ethnic groups must be considered in clinical studies of beta2AR polymorphisms in asthma.

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