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Table 3 Data in medical records and the Sweedish Maternal Health Care Register (MHCR); comparison between the two data-sets using correlation analysis, and analysis of sensitivity and specificity for binary variables

From: Internal validity of the Swedish Maternal Health Care Register

Variable Data source: Medical records Data source: MHCR Data available in both data sources Identical information in both data sources Correlationa Sensitivity Specificity
  n % n % n % n %    
Variables collected at first antenatal care (ANC) visit            
Date of first visit in ANC (numerical) 877 99.9 868 98.9 867 98.7 685 79.0 0.878 (S)   
No of previous deliveries (numerical) 878 100 867 98.7 867 98.7 840 96.8 0.971 (P)   
Maternal weight at first ANC visit (numerical) 862 98.1 855 97.4 847 96.4 798 94.2 0.990 (P)   
Maternal height (numerical) 872 99.3 862 98.2 860 97.9 834 97.0 0.982 (P)   
Smoking at first ANC visit (Yes/No) 875 99.7 872 99.2 868 98.9 843 97.1 0.742 (C) 0.650 0.995
Use of Snuff at first ANC visit (Yes/No) 878 100 871 99.2 871 99.2 861 98.9 0.540 (C) 0.429 0.998
Assessment of alcohol screening prior to pregnancy (AUDIT) (Yes/No) 802 91.3 859 97.8 788 89.7 691 87.7 0.480 (C) 0.986 0.393
If Yes, AUDIT score (numerical)b 650/643 98.9 777/771 99.2 621 95.5 600 96.6 0.989 (P)   
Variables collected at 4 to 16 weeks postpartum            
Prenatal diagnostics            
Amniocentesis (AC) (Yes/No) 875 99.7 791 90.1 788 89.7 772 98.0 0.754 (C) 0.743 0.991
Chorion Villus Sampling (CVS) (Yes/No) 875 99.7 790 90.0 787 89.6 778 98.9 0.176 (C) 0.167 0.995
Combined Ultrasound and Biochemical screening (CUB) (Yes/No) 780 88.8 791 90.1 700 89.7 665 95.1 0.888 (C) 0.936 0.957
Second trimester Serum Screening (Yes/No) 849 96.7 790 90.0 767 87.4 671 87.4 0.002 (C) 0.043 0.958
Ultrasound examination at 16 – 21 gestational weeks (Yes/No) 862 98.2 791 90.1 779 88.6 755 96.9 0.064 (C) 0.979 0.800
Estimated date of delivery (ultrasound) (numerical)c 871 99.2 874 99.5 868 98.9 781 90.0 0.946 (S)   
Oral Glucose Tolerance Test (OGTT) performed (Yes/No) 869 98.9 877 99.9 868 98.9 842 97.0 0.854 (C) 0.880 0.982
If Yes, 2-hour value of plasma glucose at OGTT (numerical)d 100/48 48.0 104/97 93.3 46 46.0 34 73.9 0.902 (P)   
Smoking at 32 gestational weeks (Yes/No) 858 97.7 876 99.8 856 97.5 849 99.1 0.864 (C) 0.821 0.998
Use of Snuff at 32 gestational weeks (Yes/No) 832 94.8 876 99.8 830 94.5 826 99.5 0.712 (C) 0.625 0.999
Maternal weight, last data entry after 35 gestational weeks (numerical) 777 88.5 843 96.0 760 86.6 706 92.9 0.989 (P)   
No. of ANC visits until estimated date of delivery (numerical) 877 99.9 868 98.9 867 98.7 627 72.3 0.915 (P)   
Date of delivery (numerical) 878 100 878 100 878 100 842 95.9 0.989 (S)   
Live born child (Yes/No) 878 100 878 100 878 100 874 99,5 0.598 (C) 0.999 0.500
Birth weight (numerical) 876 99.8 869 99.0 868 98.9 813 93.7 0.989 (P)   
Gender of infant (Boy/Girl/Sex unknown) 878 100 874 99.5 874 99.5 862 99.2 0.973 (C)   
Singleton birth/multiple births 877 99.9 878 100 877 99.8 875 99.7 0.908 (C)   
Mode of delivery (vaginal/instrumental vaginal/caesarean section) 876 99.8 876 99.8 874 99.5 857 98.0 0.946 (C)   
If caesarean section, elective CS/emergency CSe 130/115 88.5 129/128 99.2 110 84.6 102 92.7 0.841 (C)   
  1. Comparison between the two data-sets using correlation analysis, and analysis of sensitivity and specificity for binary variables.
  2. aCorrelation analysis: C = Cohen’s kappa, P = Pearson´s correlation coefficient, S = Spearman`s correlation coefficient;
  3. bMeasures are calculated for those who have undergone alcohol screening (n = 650). The denominator is the total no of “Yes” responses. Denominator in the Medical records =650. Denominator in the MHCR = 771.
  4. cMeasures are calculated for those who have undergone ultrasound.
  5. dMeasures are calculated for those who have undergone OGTT. The denominator is the total no of “Yes” responses. The denominator for the medical records = 100. The denominator for the MHCR = 104.
  6. eMeasures are calculated for those who have undergone caesarean section. The denominator is the total no of “Yes” responses. The denominator for the medical records = 130. The denominator for the MHCR = 129.