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Table 4 Comparison between primary collection and re-collection of data from medical records using correlation analysis, and analysis of sensitivity and specificity for binary variables

From: Internal validity of the Swedish Maternal Health Care Register

Variable Medical recordsa Medical records re-collectionb Data available in both data sources Identical information in both data sources Correlationc Sensitivity Specificity
  n % n % n % n %    
Variables collected at first antenatal care (ANC) visit            
Date of first visit in ANC (numerical) 150 100 150 100 150 100 116 77.3 0.773 (S)   
No of previous deliveries (numerical) 150 100 150 100 150 100 149 99.3 0.988 (P)   
Maternal weight at first ANC visit (numerical) 147 98.0 148 98.7 147 99.3 146 99.3 0.995 (P)   
Maternal height (numerical) 149 99.3 149 99.3 149 100 148 99.3 1.000 (P)   
Smoking at first ANC visit (Yes/No) 149 99.3 149 99.3 149 100 148 99.3 0.794 (C) d 1.000
Use of Snuff at first ANC visit (Yes/No) 150 100 150 100 150 100 146 97.3 0.793 (C) 0.667 1.000
Assessment of alcohol screening prior to pregnancy (AUDIT) (Yes/No) 130 86.7 130 86.7 130 86.7 121 93.1 0.729 (C) 0.972 0.136
If Yes, AUDIT score (numerical)e 113/109 96.5 108/106 98.1 102 90.3 100 98.0 0.987 (P)   
Variables collected at 4 to 16 weeks postpartum            
Prenatal diagnostics            
Amniocentesis (AC) (Yes/No) 150 100 150 100 150 100 150 100 1.000 (C) 1.000 0.983
Chorion Villus Sampling (CVS) (Yes/No) 150 100 150 100 150 100 150 100 1.000 (C) d 0.992
Combined Ultrasound and Biochemical screening (CUB) (Yes/No) 147 98.0 149 99.3 147 98.6 142 96.6 0.912 (C) 0.919 0.941
Second trimester Serum Screening (Yes/No) 148 98.7 150 100 148 98.7 148 100 f   
Ultrasound examination at 16 – 21 gestational weeks (Yes/No) 147 98.0 147 98.0 147 98.0 145 99.0 0.246 (C) 0.975 d
Estimated date of delivery (ultrasound) (numerical)g 147 100 147 100 147 100 145 98.7 0.955 (S)   
Oral Glucose Tolerance Test (OGTT) performed (Yes/No) 149 99.3 149 99.3 148 98.0 144 98.0 0.819 (C) 1.000 0.986
If Yes, 2-hour value of plasma glucose at OGTT (numerical)h 13/10 77.0 10/9 90.0 9 69.2 9 100 1.000 (P)   
Smoking at 32 gestational weeks (Yes/No) 145 96.7 145 96.7 145 100 145 100 1.000 (C) 1.000 1.000
Use of Snuff at 32 gestational weeks (Yes/No) 145 96.7 145 96.7 145 100 144 99.3 0.797 (C) 1.000 1.000
Maternal weight, last data entry after 35 gestational weeks (numerical) 142 94.7 141 94.0 141 99.3 137 97.2 1.000 (P)   
No. of ANC visits until estimated date of delivery (numerical) 150 100 150 100 150 100 96 64.0 0.890 (P)   
Date of delivery (numerical) 150 100 150 100 150 100 149 99.3 0.975 (S)   
Live born child (Yes/No) 150 100 150 100 150 100 150 100 f 1.000 1.000
Birth weight (numerical) 150 100 150 100 150 100 140 93.3 0.997 (P)   
Gender of infant (Boy/Girl/Sex unknown) 150 100 150 100 150 100 149 99.3 0.987 (C)   
Singleton birth/multiple births 150 100 150 100 150 100 150 100 1.000 (C)   
Mode of delivery (vaginal/instrumental vaginal/caesarean section) 150 100 150 100 150 100 149 99.3 0.983 (C)   
If caesarean section, elective CS/emergency CSi 23/22 95.7 23/23 100 22 95.7 22 100 1.000 (C)   
  1. aPrimary collection of data from medical records.
  2. bRe-collection of data from medical records.
  3. cCorrelation analysis: C = Cohen’s kappa, P = Pearson´s correlation coefficient, S = Spearman`s correlation coefficient.
  4. dSensitivity or specificity not possible to calculate since one or more of the cells in the calculation includes zero.
  5. eMeasures are calculated for those who have undergone alcohol screening. The denominator is the total no of “Yes” responses. Denominator in the Medical records (n = 113), denominator in the MHCR (n = 108).
  6. fCohen’s kappa is not calculated as one of the variables is a constant.
  7. gMeasures are calculated for those who have undergone ultrasound.
  8. hMeasures are calculated for those who have undergone OGTT. The denominator is the total no of “Yes” responses. Denominator for the medical records (n = 13), denominator for the MHCR (n = 10).
  9. iMeasures are calculated for those who have undergone caesarean section. The denominator is the total no of “Yes” responses. Denominator for the medical records (n = 23), denominator for the MHCR (n = 23).