[1] NU Hosp Grp, Dept Med, Uddevalla, Sweden
[2] Univ Gothenburg, Dept Mol & Clin Med, Gothenburg, Sweden
[3] Statistiska Konsultgruppen, Gothenburg, Sweden
[4] Univ Gothenburg, Sahlgrenska Acad, Inst Neurosci & Physiol, Statistiska Konsultgruppen,Dept Ophthalmol, Gothenburg, Sweden