Table 3.

Positive predictive value (PPV) of preeclampsia (PE) registration in the Medical Birth Registry of Norway (MBRN), overall (A) and in five regions of Norway (B). The gold standard (GS) for true preeclampsia was based on blood pressure and proteinuria recordings on antenatal charts and/or ICD-10 codes from hospital discharge diagnoses. Results are shown for 5340 women participating in the Norwegian Mother and Child Cohort Study and giving birth in Norway, 1999-2010.

A Overall PPV	PE in MBRN and GS	PE in MBRN only	PE in GS only	PPV	95% CI
Overall results Aa	2,936	564	95	83.9	[82.7, 85.1]
Overall results Bb	3,055	445	112	87.3	[86.2, 88.4]
B Regional results	PE in MBRN and GS	PE in MBRN only	PE in GS only	PPV	95% CI	Difference in PPV	95% CI around difference
East	467	115	23	80.2	[77.0, 83.4]	−8.2	[−11.9, −4.5]
South	676	162	31	80.7	[78.0, 83.4]	−7.7	[−10.9, −4.5]
West	1,109	145	20	88.4	[86.6, 90.2]	0	Reference
Middle	492	103	14	82.7	[79.7, 85.7]	−5.7	[−9.2, −2.2]
North	192	39	7	83.1	[78.3, 87.9]	−5.3	[−10,4 −0.2]

Abbreviations: CI, confidence interval; GS, gold standard; ICD10, International Classification of Diseases, 10^th revision; MBRN, Medical Birth Registry of Norway; PE, preeclampsia; PPV, positive predictive value

^aTrue preeclampsia was based on blood pressure increase (from antenatal charts) to at least 140 mmHg systolic and/or 90 mmHg diastolic after the 20^th week of gestation together with proteinuria of at least 0.3 g per 24 hours or ≥1 + on dip-stick; or one or more ICD 10 codes indicating preeclampsia (O14 or O15) on the hospital discharge codes.

^bAs above, but in addition the hospital discharge code O13 (ICD-10) was included as sufficient for defining a true preeclampsia case.