Estimation of spermarche from longitudinal spermaturia data.
A number of studies have dealt with determination of the age at onset of sperm emission (spermarche), based on observations of first occurrence of spermatozoa in urine. A major problem in this connection is the intermittent occurrence of sperm-negative urine samples after the achievement of spermarche. We have here considered an empirical Bayes approach for handling the probability of a sperm-positive urine sample after spermarche. The investigation was inspired by a concrete longitudinal study concerning 40 Scottish boys, which is used for illustration throughout. In this study, the urine was tested for spermatozoa from well before spermarche and every 3 months thereafter for at most 7 years. Some of the boys left the study earlier and techniques for handling such censoring were also developed.
Jørgensen
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M
Statistical Research Unit, Faculty of Medicine, University of Copenhagen, Denmark.
Keiding
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N
Skakkebaek
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NE
D000293:Adolescent; D000367:Age Factors; D001699:Biometry; D002648:Child; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D015233:Models, Statistical; D011627:Puberty / Q000652:urine*; D013094:Spermatozoa; D014556:Urine / Q000166:cytology