Liley's method: Zones and Percentage Probabilities

From the position of the infant on the Liley plot, it was possible to predict the degree of affliction of the newborn infant.

Lines to Define the Liley Plot

Lines	y at 28 weeks	y at 40 weeks	*? log (100absorbance)**
IIIA - IIIB	0.50	0.168	-0.46
IIB - IIIA	0.23	0.083	-0.44
IIA - IIB	0.12	0.04	-0.48
I - IIA	0.056	0.019	-0.45

where:

• IIIB is most severely affected and I is least.

• The absorbance at 40 weeks is about one third of the value at 28 weeks.

• The value for y at 40 weeks on line I-IIA was given as 0.30, which is obviously wrong.

Mean slope of lines: -0.039

LOG10 (100 * (absorbance)) =

= ((-0.039) * (weeks gestation)) + B

absorbance =

= (10 ^ (((-0.039) * (weeks gestation)) + B)) / 100

where:

• B for IIIA-IIIB = 2.78

• B for IIB-IIIA = 2.45

• B for IIA-IIB = 2.17

• B for I-IIA = 1.84

		Percent in each cohort with a given cord hemoglobin
Zone	Week	un-affected	Cord Hgb > 14	Cord Hgb 11 - 13.9	Cord Hgb 8 - 10.9	Cord Hgb < 8, stillborn
I	28 - 31	56	38	6
	31 - 34	52	19	29
	34 - 37	36	40	21	3
	37 - 40	33	49	18
IIA	28 - 31	25	29	28	8	10
	31 - 34	24	37	30	9
	34 - 37	14	42	34	8	2
	37 - 40	18	41	35	6
IIB	28 - 31	8	20	23	21	28
	31 - 34	6	9	19	44	22
	34 - 37		10	35	45	10
	37 - 40
IIIA	28 - 31				12	88
	31 - 34			7	29	64
	34 - 37				44	56
	37 - 40
IIIB	28 - 31					100
	31 - 34					100
	34 - 37					100
	37 - 40					100

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