Validity of a hospital-based obstetric register using medical records as reference

Figures & data

Table 1 Definition of measures of validity

Obstetric Database	Medical record (gold standard)		Total
	Present	Absent
Present	a	b	a + b
Absent	c	d	c + d
Total	a + c	b + d

Notes: The sensitivity is the proportion of patients with registration of the indicator according to both medical records and the Obstetric Database (a), compared to all patients with the indicator according to medical records (a + c) = True positive (a)/(True positive [a] + false negative [c]). The specificity is the proportion of patients without registration of the indicator according to both medical records and the Obstetric Database (d), compared to all patients without the indicator according to medical records (b + d) = True negative (d)/(True negative [d] + false positive [b]). The positive predictive value is the proportion of patients with registration of the indicator according to both medical records and the Obstetric Database (a), compared to all patients with the indicator according to the Obstetric Database (a + b) = True positive (a)/(True positive [a] + false positive [b]). The negative predictive value is the proportion of patients without registration of the indicator according to both medical records and the Obstetric Database (d), compared to all patients without the indicator according to the Obstetric Database (c + d) = True negative (d)/(True negative [d] + false negative [c]).

Table 2 Number of registrations in the Obstetric Database and in medical records and the proportion of agreement (%) for each indicator

Indicator	In the Obstetric Database		Not in the Obstetric Database		Proportion of
	In medical records	Not in medical records	In medical records	Not in medical records	agreement, %, (95% confidence interval)
Oxytocin due to dystocia	46	20	2	179	91.1 (86.8–94.3)
Epidural analgesia	68	0	3	176	98.8 (96.5–99.8)
Vacuum extraction	21	0	2	224	99.2 (97.1–99.9)
Emergency cesarean delivery	35	0	1	211	99.6 (97.8–100.0)
Elective cesarean delivery	23	1	1	222	99.2 (97.1–100.0)
Perineal tear degree 3	8	1	0	238	99.6 (97.8–100.0)
Perineal tear degree 4	0	0	0	247	100.0 (100.0–100.0)
Scalp blood pH	69	1	0	177	99.6 (97.8–100.0)
Arterial pH from the umbilical cord	221	3	3	17	97.9 (94.7–99.1)
Apgar score after 5 minutes	241	2	1	0	98.8 (96.5–99.8)
Test for gestational diabetes	84	6	9	148	93.9 (90.2–96.6)

Table 3 Sensitivity, specificity, positive, and negative predictive values (95% confidence interval) for eleven indicators in the Obstetric Database

Indicator	Sensitivity	Specificity	Positive predictive value	Negative predictive value
Oxytocin due to dystocia	0.96 (0.86–0.99)	0.90 (0.85–0.94)	0.70 (0.57–0.80)	0.99 (0.96–1.00)
Epidural analgesia	0.96 (0.88–0.99)	1.00 (0.98–1.00)	1.00 (0.95–1.00)	0.98 (0.95–1.00)
Vacuum extraction	0.91 (0.72–0.99)	1.00 (0.98–1.00)	1.00 (0.84–1.00)	0.99 (0.97–1.00)
Emergency cesarean delivery	0.97 (0.85–1.00)	1.00 (0.98–1.00)	1.00 (0.90–1.00)	1.00 (0.97–1.00)
Elective cesarean delivery	0.96 (0.79–1.00)	1.00 (0.98–1.00)	0.96 (0.79–1.00)	1.00 (0.98–1.00)
Perineal tear degree 3	1.00 (0.63–1.00)	1.00 (0.98–1.00)	0.89 (0.52–1.00)	1.00 (0.98–1.00)
Perineal tear degree 4a	–	–	–	–
Scalp blood pH	1.00 (0.95–1.00)	0.99 (0.97–1.00)	0.99 (0.92–1.00)	1.00 (0.98–1.00)
Arterial pH from the umbilical cord	0.99 (0.96–1.00)	0.85 (0.62–0.97)	0.99 (0.96–1.00)	0.85 (0.62–0.97)
Apgar score after 5 minutesb	1.00 (0.98–1.00)	0	0.99 (0.97–1.00)	0
Test for gestational diabetes	0.90 (0.82–0.95)	0.96 (0.92–0.99)	0.93 (0.86–0.98)	0.94 (0.89–0.97)

Notes:

a No perineal tear degree 4 was registered in either Obstetric Database or medical records. Therefore, statistics are not presented for this indicator;

b specificity and negative predictive value equals 0 as Apgar score after 5 minutes was always registered in either Obstetric Database or the medical record or both (no true negative).

Table 4 Prevalence of indicators in medical records by each assessor, inter-rater agreement (%) and κ coefficients (95% confidence interval) for each indicator

Indicator	Assessor 1	Assessor 2	% agreement	κ coefficient
Oxytocin due to dystocia	51	57	94.3	0.83 (0.75–0.92)
Epidural analgesia	71	71	100	1.00 (1.00–1.00)
Vacuum extraction	23	24	99.6	0.98 (0.93–1.00)
Emergency cesarean delivery	34	36	99.2	0.97 (0.92–1.00)
Elective cesarean delivery	26	24	99.2	0.96 (0.89–1.00)
Perineal tear degree 3	7	7	98.4	0.71 (0.43–0.98)
Perineal tear degree 4a	0	1	99.6	–
Scalp blood pH	68	69	99.6	0.99 (0.97–1.00)
Arterial pH from the umbilical cord	227	228	97.1	0.77 (0.61–0.94)
Apgar score after 5 minutes	242	241	99.6	0.80 (0.41–1.00)
Test for gestational diabetes	85	93	95.1	0.89 (0.84–0.95)

Note:

a It was not possible to calculate the κ coefficient for perineal tear degree 4 due to no registrations for assessor 1.