Urine Congo red test for the detection of preeclampsia in pregnant women presenting with suspected preeclampsia

Figures & data

Figure 1. Urine Congo red kit test.

Figure 2. Flow chart of study participants.

Figure 3. Proportion of the diagnosis of preeclampsia based on using the urine Congo red test.

Figure 4. Pearson correlation [with 95% confidence interval (CI)] between Congo red and proteinuria (UPCR).

Table 1. Characteristics of the study population stratified by the diagnosis of preeclampsia.

Characteristics	Non-PE group (n = 113)	PE group (n = 131)	p-value
Age (years)^a	33.0 (26.0–36.0)	35.0 (29.0–38.0)	.05
Multiparity^b	31.9% (36)	48.9% (64)	.21
BMI (kg/m^2)^a	24.1 (21.4–29.6)	24.2 (21.1–28.5)	.45
Highest SBP (mmHg)^a	145.0 (140.0–150.0)	160.0 (150.0–172.0)	<.01
Highest DBP (mmHg)^a	90.0 (86.0–94.0)	98.0 (90.0–109.0)	<.01
Proteinuria (UPCR ≥0.3 mg/dL)^b	8.8% (10)	87.8% (115)	<.01
UPCR (mg/dL)^a	0.2 (0.1–0.2)	0.9 (0.4–2.3)	<.01
Serum platelet level (x10^3/µL)^a	258.5 (217.0–308.3)	243.0 (193.0–290.0)	.04
Creatinine (mg/dL)^a	0.5 (0.5–0.6)	0.6 (0.5–0.7)	.21
AST (U/L)^a	19.0 (16.0–23.0)	20.0 (17.0–29.3)	.06
ALT (U/L)^a	14.0 (10.0–19.0)	11.0 (8.0 − 23.0)	.13
FGR^b	9.7% (11)	18.3% (24)	.06
GA at delivery (weeks)^a	38.0 (37.0–39.0)	36.0 (33.0–39.0)	<.01
Birth weight (gram)^a	2985.0 (2615.0–3275.0)	2685.0 (1728.0–3080.0)	<.01
Apgar at 1 min (Apgar score)^a	9.0 (8.0–9.0)	8.0 (6.8–9.0)	.07
Apgar at 5 min (Apgar score)^a	10.0 (9.0–10.0)	9.0 (9.0–10.0)	.09
Cesarean Delivery^b	53.1% (60)	77.9% (102)	<.01
NICU admission^b	5.3% (6)	26.7% (35)	<.01
Stillbirth^b	0.0% (0)	1.5% (2)	.19
RDS^b	1.8% (2)	12.2% (16)	<.01
IVH^b	0.0% (0)	3.8% (5)	.03
Neonatal sepsis^b	3.5% (4)	6.9% (9)	.14

^a Data are presented as median (IQR).

^b Data are presented as % (absolute number), Abbreviations. GA, gestational age; AST, aspartate aminotransferase; ALT, alanine aminotransferase; FGR, fetal growth restriction; NICU, neonatal intensive care unit; RDS, respiratory distress syndrome; IVH, intraventricular hemorrhage; BMI, body mass index; SBP, systolic blood pressure; DBP, diastolic blood pressure; UPCR, urine protein creatinine ratio.

Table 2. Frequency of urine Congo red test results in preeclampsia and non-preeclampsia groups.

Urine Congo red test^a	Non-PE group (n = 113)	PE group (n = 131)
≥2+	108	130
≥3+	47	80
≥4+	6	65
≥5+	4	59
≥6+	2	53
≥7+	1	38
8+	0	5

^a Data are presented as absolute number.

Table 3. Performance of the urine Congo red test for the prediction of preeclampsia.

Urine Congo red Result	Odds Ratio [95%CI]	Sensitivity (%) [95%CI]	Specificity (%) [95%CI]	Positive LR [95%CI]	Negative LR [95%CI]	PPV (%) [95%CI]	NPV (%) [95%CI]
≥ 2+	6.0 [0.7 − 52.3]	99.2 [95.8 − 100]	4.4 [1.5 − 10.0]	1.0 [1.0 − 1.1]	0.2 [0.2 − 1.5]	54.6 [48.1 − 61.1]	83.3 [35.9 − 99.6]
≥ 3+	2.2 [1.3 − 3.7]	61.1 [52.2 − 69.5]	58.4 [48.8 − 67.6]	1.5 [1.1 − 1.9]	0.7 [0.5 − 0.9]	63.0 [54.0 − 71.4]	56.4 [46.9 − 65.6]
≥ 4+	17.6 [7.4 − 41.8]	49.6 [40.8 − 58.5]	94.7 [88.8 − 98.0]	9.3 [4.2 − 20.7]	0.5 [0.4 − 0.6]	91.5 [82.5 − 96.8]	61.8 [54.2 − 69.1]
≥ 5+	22.3 [8.1 − 61.5]	45.0 [36.3 − 54.0]	96.5 [91.2 − 99.0]	12.7 [4.8 − 33.9]	0.6 [0.5 − 0.7]	93.7 [84.5 − 98.2]	60.2 [52.7 − 67.4]
≥ 6+	37.7 [8.9 − 159.3]	40.5 [32.0 − 49.4]	98.2 [93.8 − 99.8]	22.9 [5.7 − 91.7]	0.6 [0.5 − 0.7]	96.4 [87.5 − 99.6]	58.7 [51.4 − 65.8]
≥ 7+	45.8 [6.2 − 339.7]	29.0 [21.4 − 37.6]	99.1 [95.2 − 100]	32.8 [4.6 − 235.0]	0.7 [0.6 − 0.8]	97.4 [86.5 − 99.9]	54.6 [47.6 − 61.6]
≥ 8+		3.8 [1.3 − 8.7]	100.0 [96.8 − 100.0]		1.0 [0.9 − 1.0]	100 [47.8 − 100]	47.3 [40.8 − 53.8]

Abbreviations. CI, confidence interval; LR, likelihood ratio; PPV, positive predictive value; NPV, negative predictive value.

Data availability statement

The data that support the findings of this study are available from the corresponding author, P.T., upon reasonable request.