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Title: Reliability of the atd Angle in Dermatoglyphic Analysis
Authors and Institutions:
Emily K. Brunson1
Darryl J. Holman1
Laura L. Newell-Morris1
Christina M. Giovas1
Ann Striessguth2
1Department of Anthropology
2Department of Psychiatry and Behavioral Sciences
University of Washington
Seattle, WA 98195
Total Number of Pages: 16 Number of Figures: 1 Number of Tables: 2 Abbreviated title: Reliability of the atd angle Send Proof to:
Emily K. Brunson Department of Anthropology Box 353100 University of Washington Seattle, WA 98195-3100 USA Fax: (206) 543-3285 Email: [email protected]
Keywords: atd angle, dermatoglyphics, reliability
2 Brunson, et al.
ABSTRACT
The atd angle is a dermatoglyphic trait formed by drawing lines between the triradii below the
first and last digits and the most proximal triradius on the hypothenar region of the palm. This trait has
been widely used in dermatoglyphic studies, but several researchers have questioned its utility,
specifically whether or not it can be measured reliably. In this paper, we examine the measurement
reliability of this trait.
Finger and palm prints were taken using the carbon paper and tape method from 287
individuals with in utero exposure to alcohol and 175 unexposed controls. A sample of 100 matched
(right and left) prints was constructed from 75 randomly selected controls and 25 randomly selected
cases. Each atd angle was read twice, at different times, by Reader A, using a goniometer and a
magnifying glass, and three times by a Reader B, using Adobe Photoshop. Inter-class correlation
coefficients were estimated for the intra- and inter-reader measurements of the atd angles.
Reader A was able to quantify atd angles on 149 out of 200 prints (74.5%), and Reader B on
179 out of 200 prints (89.5%). Both readers agreed on whether an angle existed on a print 89.8% of
the time for the right hand and 78.0% for the left hand. Intra-reader correlations were 0.97 or greater
for both readers. Inter-reader correlations for atd angles measured by both readers ranged from 0.92
to 0.96. These results suggest that the atd angle can be measured reliably, and further imply that
measurement using a software program with an angle measurement tool to measure the angle on
digitized prints may improve this reliability.
3 Brunson, et al.
Dermatoglyphic traits are widely used markers in analyses of fetal development, developmental
disturbances, disease and genetics (e.g. Woolf and Gianas, 1976; David, 1981(b); Pursnani et al.,
1989; Arrieta et al., 1990; Wolman et al., 1990; Balgir, 1993; Balgir et al., 1993; Kohli and Bhalla,
2000; Paez et al., 2001; Neiswanger et al., 2002; Avila et al., 2003; Milicic et al., 2003). Most
dermatoglyphic traits develop in utero during weeks 17 through 24 and remain unchanged during an
individual’s lifetime (Babler, 1991). Therefore, analyses of dermatoglyphic traits can provide
information on intrauterine disturbances and possibly even genetic abnormalities (Babler, 1991;
Chakraborty, 1991; Meier, 1991). The most commonly analyzed dermatoglyphic traits include
descriptions of finger and hypothenar patterns, measurements of ridge counts between triradii (points
formed by the convergence of three patterns of ridges) and measurement of the atd angle, the angle that
exists between the a, d, and t triradii on the palm (Figure 1).
Although the atd angle has been widely used in dermatoglyphic studies, several researchers
have questioned its utility, specifically whether or not it can be measured reliably (Cummins and Mildo,
1961; Sharma, 1964; Mavalwala, 1979; Priest, 1979; David, 1981a). Measurement of the atd angle
involves locating three triradii and then measuring the angle between these points. Each step in this
process increases the possibility of reader error, including inconsistent identification of landmarks.
Measurement of atd angles is occasionally further complicated by the presence of additional a, d or t
triradii on some prints.
The purpose of our research was to determine the reliability of atd angle measurements within
and between readers. We also examined the literature in which results from the analyses of atd angles
4 Brunson, et al.
were reported in order to assess the consistency of associations between atd angles and developmental,
disease and genetic conditions of interest.
MATERIALS AND METHODS
Palm prints were taken using the carbon paper and tape method (Aase and Lyons 1971) from
287 individuals with in utero exposure to alcohol and 175 unexposed controls. A sample of 100
matched (right and left) prints was constructed from 75 randomly selected controls and 25 randomly
selected cases. We chose to include both affected and unaffected subjects in this sample because this is
a typical design for studies using the atd angle.
Atd angles from these 200 prints were read by two readers (A and B) using the criteria set forth
for atd angle measurement by Elbualy and Schindeler (1971). Each angle was read twice by Reader A,
through the process of placing enlarged photocopies of the prints into a transparent plastic sleeve,
locating and marking the a, d and t triradii on the sleeve, and drawing straight lines from a to t and from
d to t. The atd angle was then read to the nearest degree using a basic goniometer. Reader B read
each angle three times from images created by digitally scanning each print at a resolution of 400 dots
per in (DPI). The prints were digitally enlarged so that the a, d and t triradii could be marked, and then
the Photoshop (version 8.0, Abobe Systems, Inc., San Jose, CA) angle measurement tool was used to
measure the resulting angle. All angle measurements were rounded to the nearest degree.
To increase independence between successive measurements of the prints, each set of readings
was made at different times, weeks or months apart. Markings from previous readings were not saved
5 Brunson, et al.
by either reader to ensure that subsequent readings were completely independent. Prints were read in a
random order; and right and left prints from the same individual were not read at the same time.
When two a or two d triradii were encountered, the more radial and more ulnar triradius,
respectively, was used to determine the angle. When more than one t triradius was encountered in a
single print, only the more proximal triradius was used (t instead of t’ and t’ instead of t”) in accordance
with the methods proposed by David (1981a).
To determine if the two readers measured the same atd angle, we used a type of randomization
test. For each print, we randomly selected one of the two readings from Reader A and one of three
readings from Reader B. A two-tailed t-test (α=0.05) was used to test whether the mean of the
difference between pairs of readings (Reader A - Reader B) was significantly different from zero. We
repeated this procedure one million times, and counted the number of times the sum of the difference
was significantly different from zero. Intraclass correlation coefficients (ICC) were then estimated to
determine the degree of association within and between readers.
RESULTS
Triradii were not readable on all prints; therefore, atd angles could not be determined for all
200 prints. Reader A was able to read atd angles on 149 out of 200 prints (74.5%), and Reader B
was able to read the angles on 179 out of 200 prints (89.5%). Both readers agreed on whether an
angle existed on a print 89.8% of the time on the right hand and 78.0% on the left hand.
For angles that both readers were able to measure, Reader A’s readings tended to be slightly
higher (mean 45.6°) than Reader B’s (mean 44.8°), but Reader A’s readings were less variable (SD
6 Brunson, et al.
6.3°, compared to SD 7.4° for Reader B). These trends remained true even when measurements from
the right and left hands were examined separately (Table 1). The randomization test yielded no
significant differences (0 of 1,000,000 times) strongly suggesting that Reader A’s and Reader B’s
readings are interchangeable—that is, the slight upward bias in Reader A’s readings relative to Reader
B’s readings is not significant.
Reliability within readers, as assessed by the ICC analysis, showed that both readers were
consistent in their measurements. Reader A had an ICC of 0.97 and Reader B had an ICC of 0.99 for
all three pairwise comparisons (reading 1 vs. reading 2, reading 1 vs. reading 3, and reading 2 vs.
reading 3). Considering the reliability of atd angle measurements between readers, the ICC analysis
suggested that there is more variability between readers than within the same reader, but that the
correlations were still well above 0.9, ranging from 0.92 to 0.96 (Table 2).
DISCUSSION
The purpose of this study was to assess the reliability of measuring the atd angle. The high
ICCs obtained in our analysis suggest that atd angles can be measured reliably both within and between
readers. The results of the randomization test further suggest that two different readers, using different
measurement tools (a goniometer versus a digital angle measurement tool), can measure atd angles
without bias. These findings lend support for a trait that has been widely used in the literature on birth
defects, neurological disorders and diseases. A reader who is well-trained in recognizing the landmarks
and measuring the angle should provide results consistent with those of other readers equally well-
trained.
7 Brunson, et al.
In addition, our findings lend support for the method of using software programs, such as
Adobe Photoshop, to measure dermatoglyphic traits on digitized images. Using such a method, Reader
B was able to measure atd angles on 30 more prints (15% of the total sample) compared to Reader A,
who used a magnifying glass and goniometer to measure the angles on photocopies of the prints.
Additionally, while the intra-observer ICCs were high (>0.97) for both readers, correlations were
consistently higher for Reader B. Because both readers were trained using the same methods and
because they cross-checked their methods during training to ensure they were reading the prints with the
same methods and a comparable level of accuracy, the differences in the number of prints each reader
was able to read and the differences in the intra-observer ICCs between the readers likely reflect the
difference in the tools each reader used to measure atd angles on the prints.
It seems from our analysis that reading the prints in a digital format provided the best results.
Not only did using Photoshop allow for the prints to be magnified and the lines of the palms to be
enhanced when necessary, but the angle measurement tool in this program also reduced the error that
could occur from a reader misreading an angle on a goniometer. We recommend that in the future
researchers consider digitally scanning the prints and then using some type of software program to
digitally measure the atd angle and even other dermatoglyphic traits. We used an ordinary flat-bed
scanner to scan the images at 400 DPI using an eight-bit grayscale.
While we have shown that the atd angle can be measured reliably, the question still remains as
to whether or not the atd angle is useful in applied studies. We reviewed the current literature in which
atd angles have been used to investigate a variety of conditions, including autism (Arrieta et al., 1990;
Wolman et al., 1990; Milicic et al., 2003), schizophrenia (Balgir et al., 1993; Paez et al., 2001; Avila et
8 Brunson, et al.
al., 2003), cleft lip/palate (Woolf and Gianas, 1976; Balgir, 1993; Kohli and Bhalla, 2000; Neiswanger
et al., 2002) and genetic heart conditions (David, 1981(b); Pursnani et al., 1989). The results of these
studies were largely contradictory, with more than half finding no differences in the atd angles of
subjects with a given condition versus unaffected controls. When associations were found, the direction
of the relationship often differed between studies: for example Wolman and colleagues (1990) found no
difference between atd angles in children with and without autism; Arietta and colleagues (1990) found
atd angles were wider in autistic girls, but that there was no difference between normal controls and
autistic boys; while Milicic and colleagues (2003) found atd angles were wider among autistic boys, but
not autistic girls, when compared to normal controls.
While it is possible that measurement error resulting from multiple or untrained readers is
responsible for these contradictory results, we suggest that factors other than reader reliability should
also be considered as possible causes for the discrepancies. First, it is important to consider that atd
angles change with age (the angle is larger in children than adults) and with sex (the angle is larger in men
than in women; Cummins and Mildo, 1961). If these two variables are not taken into consideration,
biases may result if the age or sex-composition of the samples differs among studies. Mavalwala (1979)
has also shown that if a print is made with the fingers together, a different atd angle measurement will be
obtained than if the angle is measured from the same person with their fingers spread apart. Thus,
researchers must also be careful in obtaining consistent hand adduction during collecting the handprints.
Finally, David (1971, 1981a) has shown that great care must be taken in determining which angle to
measure (atd, at’d or at’’d). If researchers are not measuring the angle from the same t triradius, it is
impossible to determine whether the atd angle is smaller or larger because the t triradius is actually
9 Brunson, et al.
displaced or because the researchers were simply measuring the prints differently. Like David (1981a),
we suggest that researchers use the most proximal t triradius available, as this most likely represents the
“true” t triradius and not just an overabundance of hypothenar patterns. We strongly recommend that
researchers use the procedures of Mavalwala and David so that results among studies will be
comparable.
CONCLUSION
Based on the results of this research, we suggest that the atd angle can be measured reliably
whether the readings are made by individual or multiple readers and that the reliability of this
measurement may be improved by reading digitized prints with the help of a software program such as
Adobe Photoshop. Our review of the current literature showed that the atd angle provides inconsistent
relationships with traits like autism and schizophrenia. While several possibilities exist for these
discrepancies, based on the results of our study, we suggest that the usefulness of the atd angle in
dermatoglyphic studies may be increased if researchers agree on a set of methods for print collection
and measurement.
ACKNOWLEDGMENTS
We thank Carrie Kuehn for her work in collecting some of the prints used in this study. This
research was supported by a grants from NIH NIAAA (R21-AA013704 and R37-AA01455) and a
grant from the Alcohol and Drug Abuse Institute, University of Washington.
10 Brunson, et al.
LITERATURE CITED
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autistic Basque children. American Journal of Medical Genetics 35:1-9.
Avila MT, Sherr J, Valentine LE, Blaxton TA, Thaker GK. 2003. Neurodevelopmental interactions
conferring risk for schizophrenia: A study of dermatoglyphic markers in patients and relatives.
Schizophrenia Bulletin 29:595-605.
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New York: Dover Publications Inc.
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David TJ. 1981(a). The corrected atd angle. Human Heredity 31:283-285.
David TJ. 1981(b). Dermatoglyphs in congenital heart disease. Journal of Medical Ethics 18:344-
349.
Elbualy MS, Schindeler JD. 1971. Handbook of Clinical Dermatoglyphics. Coral Gables, FL:
University of Miami Press.
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cleft palate patients. Man in India 80: 185-193.
Mavalwala J. 1979. The atd angle: A critique. Birth Defects: Original Article Series 15:169-172.
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Spence MA, Marazita ML. 2002. Cleft lip with or without cleft palate and dermatoglyphic
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5:140-146.
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24:28-32.
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15:173-176.
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Indian Heart Journal 41:119-122.
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corresponding different single angular values of angle atd. Eastern Anthropologist 17:23-30.
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13 Brunson, et al.
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14 Brunson, et al.
Table 1. Summary statistics for atd angle measurements by reader
Reader* A1 A2 B1 B2 B3 right hand data
mean 45.6 46.8 45.4 45.7 45.6 SD 6.7 6.8 8.0 8.0 7.9 CV 14.7 14.5 17.6 17.5 17.3 minimum 36 37 33 33 33 maximum 73 74 80 80 78 number 77 77 77 77 77
left hand data
mean 45.2 46.1 44.4 44.7 44.5 SD 5.8 5.8 6.0 6.1 6.1 CV 12.8 12.6 13.5 13.6 13.7 minimum 35 36 35 35 36 maximum 65 66 65 65 65 number 71 71 71 71 71 * A1= Reader A’s first reading, B1= Reader B’s first reading
15 Brunson, et al.
Table 2. Reliability coefficients for atd angle measurements.
intra-observer reliability
Reader* A1 / A2 B1 / B2 B1/B3 B2/B3 right hand 0.97 0.99 0.99 0.99 left hand 0.97 0.99 0.99 0.99 inter-observer reliability
A1 / B1 A1 / B2 A1/B3 A2 / B1 A2 / B2 A2/B3 right hand 0.96 0.96 0.96 0.94 0.95 0.95 left hand 0.96 0.96 0.96 0.92 0.92 0.92 * A1= Reader A’s first reading, B1= Reader B’s first reading
16 Brunson, et al.
FIGURE CAPTIONS
Figure 1. Landmarks used to measure atd angle.
17 Brunson, et al.