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Table 1 Baseline characteristics of participants with sporadic (s-PCT), familial (f-PCT) and unclassified PCT compared to the reference population (2000 to 2016, 18 years or older)

From: Porphyria cutanea tarda increases risk of hepatocellular carcinoma and premature death: a nationwide cohort study

Characteristics s-PCT
(n = 255)
f-PCT
(n = 255)
Unclassified PCT
(n = 102)
Reference
(n = 5452,010)
n Valid % N Valid % n Valid % n Valid %
Sex – male 125 49.0 122 47.9 46 45.1 2713,666 50.2
Age in years at study start (mean, SD) 52.8 (10.9) 47.5 (13.7) 60.1 (13.9) 38.9 (22.2)
Highest level of education obtained
 Not specified 4 1.6 2 0.8 0 0 649,456 11.9
 No schooling, primary/middle education (year 1–10) 90 35.3 55 21.6 46 45.1 1334,399 24.8
 Upper secondary education (11–12, 13 or 14 years) 124 48.6 123 48.2 43 42.2 1994,025 36.6
 Tertiary education (14+ years) 37 14.5 75 29.4 13 12.8 1474,130 27.0
Lifestyle factors
 Alcohol use (yes) 163 93.6 173 93.5 35 87.5   
 Alcohol – amount of standard drinks per week (mean, SD) 1.7 (1.3) 1.6 (1.3) 1.5 (1.3)   
 Tobacco: cigarettes (yes) 83 32.6 50 19.6 30 61.2   
  Never smoked / have quit 65 37.8 127 69.4 22 53.63   
  Occasional smokers/ daily smokers 107 62.2 56 30.6 19 46.3   
 Amount of cigarettes consumed per day (mean, SD) 2.8 (6.2) 1.2 (3.8) 1.7 (4.6)   
 Body mass index (BMI)
 Underweight (BMI Under 18.5) 8 4.8 5 2.8 2 5.1   
 Normal (BMI between 18.5 and 25) 67 40.4 56 30.9 13 33.3   
 Overweight (BMI between 25 and 30) 68 41.0 90 49.7 21 53.8   
 Obese (BMI of 30 or greater) 23 13.9 30 16.6 3 7.7   
Other diseases
 Liver disease 24 11.0 12 5.2 6 5.2   
 Haemochromatosis 11 5.1 12 5.2 2 4.1   
 Type II diabetes 11 5.1 3 1.3 2 7.4   
Biochemical characteristics
 Total porphyrins (mean, 95% CI) 880.5 803.6–957.5 941.6 835.7–1047.5 989.2 660.58–1317.81   
 Uroporphyrin (mean, 95% CI) 608.5 553.5–663.4 706.1 625.03–787.1 768.45 504.01–1032.89   
  1. Abbreviations: PCT porphyria cutanea tarda
  2. Lifestyle factors are based on self-reported questionnaires sent to the Norwegian Porphyria Registry. 500 of 612 responded to the questionnaire. Biochemical characteristics are based on the highest ever recorded value (generally at time of diagnosis). Urinary porphyrins were expressed in nmol/mmol creatinine (upper reference limit < 30).