TY - JOUR

T1 - Estimation of individual reference intervals in small sample sizes

AU - Hansen, Ase Marie

AU - Garde, Anne Helene

AU - Eller, Nanna Hurwitz

AU - Hansen, Åse Marie

PY - 2007

Y1 - 2007

N2 - In occupational health studies, the study groups most often comprise healthy subjects performing their work. Sampling is often planned in the most practical way, e.g., sampling of blood in the morning at the work site just after the work starts. Optimal use of reference intervals requires that the population, on which the reference interval is based, is representative for the study group in question. The International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) recommends estimating reference interval on at least 120 subjects. It may be costly and difficult to gain group sizes of that order of magnitude for all topics in question. Therefore, new methods to estimate reference intervals for small sample sizes are needed. We present an alternative method based on variance component models. The models are based on data from 37 men and 84 women taking into account biological variation from various variables such as gender, age, BMI, alcohol, smoking, and menopause. The reference intervals were compared to reference intervals calculated using IFCC recommendations. Where comparable, the IFCC calculated reference intervals had a wider range compared to the variance component models presented in this study. The presented method enables occupational health researchers to calculate reference intervals for specific groups, i.e. smokers versus non-smokers, etc. In conclusion, the variance component models provide an appropriate tool to estimate reference intervals based on small sample sizes.

AB - In occupational health studies, the study groups most often comprise healthy subjects performing their work. Sampling is often planned in the most practical way, e.g., sampling of blood in the morning at the work site just after the work starts. Optimal use of reference intervals requires that the population, on which the reference interval is based, is representative for the study group in question. The International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) recommends estimating reference interval on at least 120 subjects. It may be costly and difficult to gain group sizes of that order of magnitude for all topics in question. Therefore, new methods to estimate reference intervals for small sample sizes are needed. We present an alternative method based on variance component models. The models are based on data from 37 men and 84 women taking into account biological variation from various variables such as gender, age, BMI, alcohol, smoking, and menopause. The reference intervals were compared to reference intervals calculated using IFCC recommendations. Where comparable, the IFCC calculated reference intervals had a wider range compared to the variance component models presented in this study. The presented method enables occupational health researchers to calculate reference intervals for specific groups, i.e. smokers versus non-smokers, etc. In conclusion, the variance component models provide an appropriate tool to estimate reference intervals based on small sample sizes.

KW - Adult

KW - Age Factors

KW - Data Interpretation, Statistical

KW - Female

KW - Health Status

KW - Humans

KW - Male

KW - Middle Aged

KW - Models, Statistical

KW - Occupational Health

KW - Reference Values

KW - Sample Size

KW - Sex Factors

U2 - 10.1016/j.ijheh.2007.01.012

DO - 10.1016/j.ijheh.2007.01.012

M3 - Journal article

C2 - 17270494

VL - 210

SP - 471

EP - 478

JO - International Journal of Hygiene and Environmental Health

JF - International Journal of Hygiene and Environmental Health

SN - 1438-4639

IS - 3-4

ER -