Diagnostic Index for Down Syndrome

Parameters in the original score:

(1) digital patterns - subscore I

(2) palms and soles (hallucal area of foot) - subscore II

(3) stigmata - subscore III

 

Parameters regrouped to make implementation easier:

(1) digital patterns

(2) hallucal area of foot

(3) other findings on hands and eyes

 

Digital Patterns

 

Digital patterns - from left and right sides:

(1) A (arch)

(2) R (radial loop, opening to radial side)

(3) U (ulnar loop, opening to ulnar side)

(4) W (whorl)

 

Patterns	Digit 1	Digit 2	Digit 3	Digit 4	Digit 5
RR	-0.48	-1.54	-0.89	0.89	1.42
AR or RA	0.19	-1.54	-0.89	0.65	1.42
AA	0.19	-0.80	-0.89	-0.24	-0.37
WR or RW	-0.48	-1.54	-0.17	0.30	1.42
WA or AW	0.19	0.61	-0.17	0.23	0.14
WW	-0.30	-0.73	-0.17	-0.24	0.14
UR or RU	-0.48	-0.84	-0.61	0.89	1.42
UA or AU	0.19	0.61	-0.61	0.23	-0.02
UW or WU	-0.10	0.61	-0.29	-0.17	-0.10
UU	0.12	0.61	0.12	0.07	-0.02

 

Hallucal Area of Foot

 

Pattern:

(1) AT (arch tibial)

(2) VDL (vestigial loop)

(3) SDL (distal loop with < 21 ridges)

(4) LDL (distal loop with >= 21 ridges)

(5) W (whorl)

(6) other (any pattern not AT, VDL, SDL, LDL or W)

 

Pattern 1	Pattern 2	Points
AT	AT	2.20
AT	any not AT (VDL, SDL, LDL, W, other)	1.31
VDL	VDL	1.28
VDL	any except AT or VDL (SDL, LDL, W, other)	1.28
SDL	SDL	0.42
SDL	any not AT or VDL or SDL (LDL, W, other)	-0.22
LDL	LDL	-0.52
LDL	W	-1.03
LDL	other	-1.82
W	W	-1.88
W	other	-1.82
other	other	-1.82

 

Other Findings

 

Findings:

(1) Brushfield spots (small, white spots at the periphery of the iris)

(2) simian crease (single transverse palmar crease rather than distinct proximal and distal palmar creases)

(3) axial triradius (ratio of hypothenar length to palmar length >= 0.4, where the lengths are taken parallel to the longitudinal axis of the arm, the hypothenar length from the distal wrist crease to the most distant point of the hypothenar eminence, and the palmar length from the distal wrist crease to the base of the third finger)

(4) thenar I1 pattern (palmar surface over distal first metacarpal)

(5) I3 pattern (outward loop below fourth finger anchored at the interdigital spaces)

(6) single crease digit 5 (palmar surface over interphalangeal joints, rather than 2)

 

Parameter	Finding	Points
Brushfield spots	bilateral	0.70
	unilateral	0.70
	none	-0.25
Simian crease	bilateral	0.36
	unilateral	0.36
	none	-0.19
axial triradius	bilateral	1.11
	unilateral	0.35
	none	-1.03
thenar I1 pattern	bilateral	-1.29
	unilateral	-0.38
	none	0.04
I3 pattern	bilateral	0.38
	right only	0.09
	left only	-0.40
	none	-0.56
single crease digit 5	bilateral	1.66
	unilateral	1.66
	none	-0.06

 

total score =

= SUM(points for all 5 digits) + (points for hallucal area) + (points for all 6 other findings)

 

Interpretation:

• minimum score: around -8.5

• maximum score: around +9.0

• If the score is > 1.99, then the patient has Down syndrome.

• If the score is < -1.54, then the patient does not have Down syndrome.

 

Score	Probability Down
-1.14	5%
-0.72	10%
-0.36	25%
0.14	50%
0.57	75%
0.97	90%
1.28	95%

from Figure 2, page 51

 

When this data is applied over the range of -1.14 to 1.28 the probability can be approximated as:

 

probability of Down syndrome =

= (-0.132445 * ((score)^3)) + (0.0476 * ((score)^2)) + (0.5613 * (score)) + 0.432

 

Below -1.14 the equation gives falsely high values.