Creatinine clearance estimation in the extremely elderly subjects

It has been reported that elderly outpatients take at least 6 different kinds of medication.To know which formula will best predict creatinine clearance, because 24-hour urine collection is difficult for elderly outpatients.We compared four types of formulae (Cockcroft and Gault, Yasuda, Orita, Walser) to estimate creatinine clearance using serum creatinine of 143 elderly inpatients (73 men, 70 women, mean age 82.9 +/- 8.6 years old) including 67 extremely elderly people with various underlying diseases.The formula of Cockcroft and Gault showed the best correlation with creatinine clearance in the extremely elderly subjects (r = 0.74) as well as in people under 85 years (r = 0.76). However, the estimated values of the extremely elderly women were lower than actual creatinine clearance.The formula of Cockcroft and Gault is the best predictive equation of creatinine clearance, except in the extremely elderly women.