Validation of the foot length measure as an alternative tool to identify low birth weight and preterm babies in a low-resource setting like Nepal: a cross-sectional study

Table 2 Sensitivity, specificity, and predictive values of a range of foot length cutoffs

Outcome	Foot length (cm) ^a	Sensitivity	Specificity	Initial criterion for cutoff (Specificity + Sensitivity) ½ ^b	Adjusted criterion for cutoff (Specificity ² + Sensitivity) ½ ^c	LR+	LR-	PPV	NPV
Low birth weight (<2000 grams)	6.7	24.1	99.0	49.1	74.0	24.1	0.8	79.0	97.0
	6.8	24.1	98.9	49.0	73.8	17.2	0.8	73.0	97.0
	6.9	31.0	98.2	53.4	75.8	17.2	0.7	68.0	97.0
	7.0	34.5	97.6	66.1	76.6	14.4	0.7	60.9	97.6
	7.1	72.4	90.8	81.6	84.7	7.9	0.3	28.9	99.0
	7.2	75.9	90.3	83.1	85.5	7.8	0.3	27.8	99.1
	7.3	75.9	88.6	82.3	84.2	6.7	0.3	24.7	99.1
	7.4	79.3	86.8	83.1	84.3	6.0	0.2	22.1	99.2
	7.5	82.8	85.2	84.0	84.4	5.6	0.2	20.2	99.4
	7.6	93.1	60.1	76.6	71.1	2.3	0.1	8.6	99.7
	7.7	93.1	55.9	74.5	68.3	2.1	0.1	7.8	99.7
Preterm (<37 weeks)	7.0	17.3	97.4	57.4	70.7	6.7	0.8	32.2	94.3
	7.1	26.9	89.6	58.3	68.7	2.6	0.8	15.6	94.5
	7.2	26.9	88.9	57.9	68.0	2.4	0.8	14.7	94.5
	7.3	26.9	87.1	57.0	67.0	2.1	0.8	12.9	94.4
	7.4	30.8	85.4	58.1	67.2	2.1	0.8	13.1	94.5
	7.5	32.7	83.8	58.3	66.7	2.0	0.8	12.6	94.6
	7.6	67.3	60.4	63.9	62.7	1.7	0.5	10.8	96.3
	7.7	73.1	56.4	64.8	62.0	1.7	0.5	10.7	96.7
	7.8	76.9	53.9	65.4	61.6	1.7	0.4	10.6	97.0
	7.9	78.8	48.8	63.8	58.8	1.5	0.4	9.9	97.0
	8.0	80.8	47.1	64.0	58.4	1.5	0.4	9.8	97.2

^aFoot lengths measured with hard plastic ruler.
Sensitivity, specificity, average of sensitivity + specificity, likelihood ratios, and predictive values were determined using non-parametric receiver operating characteristics analysis.
^bInitial criterion for cutoff (Specificity + Sensitivity) ½ is the average of specificity and sensitivity
^cAdjusted criterion for cutoff (Specificity²+ Sensitivity) ½ is the sum of average of square of specificity and sensitivity.

ISSN: 1471-2431