A point of care test for the determination of amniotic fluid interleukin-6 and the chemokine CXCL-10/IP-10

Figures & data

Table 1. Comparison of assay characteristics between ELISA and lateral flow-based immunoassay point of care test (POC).

	Interleukin-6 ELISA	Interleukin-6 point of care test	IP-10 ELISA	IP-10 point of care test
Assay time	5 h	20 min	5 h	20 min
Sample volume	12 μl	100 μl	10 μl	100 μl
Sensitivity	<0.70 pg/ml	50 pg/ml	1.67 pg/ml	100 pg/ml
Range of detection	3.13–300 pg/ml	50–10 000 pg/ml	7.8–500 pg/ml	50–10 000 pg/ml
Intra-assay coefficients of variation	2.9%	12.1%	2.8%	12.1%
Inter-assay coefficients of variation	2.8%	15.5%	3.5%	15.5%

IP-10 or CXCL-10: interferon-γ – inducible protein 10.

ELISA, enzyme-linked immunosorbent assay.

Table 2. Characteristics of study populations.

	Preterm labor (n = 20)
Age (years)	22 (20–25)
Nulliparity	40% (8/20)
Body mass index (kg/m^2)	23.3 (21.1–32.3)
Gestational age at amniocentesis (weeks)	30.5 (28.3–31)
Gestational age at delivery (weeks)	26.3 (31.5–39.2)
Birthweight (g)	2617 (1,718–3,002)
Amniotic fluid glucose (mg/dl)	25 (17–30)
Amniotic fluid white blood cell (cell/mm^3)	0 (0–5)
Amniotic fluid IL-6 ELISA (ng/ml)	1.2 (0.5–6.9)
Amniotic fluid IL-6 point of care test (ng/ml)	0.4 (0.2–1.6)
Amniotic fluid IP-10 ELISA (ng/ml)	1.8 (0.9–3.8)
Amniotic fluid IP-10 point of care test (ng/ml)	1.8 (1.3–3.2)
Placental lesions associated with amniotic fluid  infection*	42% (8/19)

Data presented as % (N) or median (interquartile range).

IL, interleukin; IP, interferon-γ – inducible protein 10 or CXCL 10; MIAC, microbial invasion of the amniotic cavity microbial; ELISA, enzyme-linked immunosorbent assay.

*Placental lesions associated with amniotic fluid infection include acute chorioamnionitis and funisitis.

Figure 1. Bland–Altman plot: direct comparison between enzyme-linked immunosorbent assay (ELISA) and lateral flow-based immunoassay point of care (POC) amniotic fluid (AF) interleukin-6 (IL-6) techniques. AF IL-6 concentrations from three patients with preterm labor with microbial invasion of the amniotic cavity (MIAC) were excluded. SD, standard deviation.

Figure 2. Amniotic fluid (AF) concentrations of interleukin-6 (IL-6) determined by enzyme-linked immunosorbent assay (ELISA) (square) and a lateral flow-based immunoassay point of care (POC) test (circle) of patients with preterm labor. Lateral flow-based immunoassay POC AF IL-6 concentrations were significantly lower than those of ELISA in every pair samples.

Figure 3. Amniotic fluid (AF) interleukin-6 (IL-6) scatter diagram with linear regression line (red line). Dashed line indicates 95% confidence interval. AF IL-6 concentrations from three patients with preterm labor with microbial invasion of the amniotic cavity (MIAC) were excluded.

Figure 4. Bland–Altman plot: direct comparison between enzyme-linked immunosorbent assay (ELISA) and lateral flow-based immunoassay point of care (POC) amniotic fluid (AF) interferon-γ – inducible protein 10 (IP-10 or CXCL 10) techniques. SD, standard deviation.

Figure 5. Amniotic fluid (AF) concentrations of interferon-γ – inducible protein 10 (IP-10 or CXCL-10) determined by enzyme-linked immunosorbent assay (ELISA) (square) and lateral flow-based immunoassay point of care (POC) test (circle) of patients with preterm labor.

Figure 6. Amniotic fluid (AF) interferon-γ – inducible protein 10 (IP-10 or CXCL-10) scatter diagram with linear regression line (red line). Dashed line indicates 95% confidence interval.