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Overview :
Ross et al developed a risk scoring system based on logistic
regression to identify women at risk for preterm delivery. 22 factors based on
historical or current gestational data were identified as significant. Women may
be identified based on a logistic score or number of risk factors present.
Patient population:
• Involved
8,240 patients delivering at Harbor/UCLA Medical Center in Los Angeles.
• The
population was predominantly Hispanic.
• Data was
collected from July, 1979 to December 1982.
|
Historic
Factor |
Univariate Odds
Ratio |
Logistic Odds
Ratio |
Regression
Coefficient |
|
previous induced abortion |
1.64 |
1.309 |
0.269 |
|
habitual abortions |
3.31 |
2.210 |
0.793 |
|
previous premature delivery |
3.09 |
2.488 |
0.912 |
|
previous neonatal death |
2.19 |
1.277 |
0.244 |
|
uterocervical anomaly |
5.26 |
1.489 |
0.398 |
|
classic Caesarean section |
2.11 |
1.600 |
0.470 |
|
previous myomectomy |
46.0 |
22.847 |
3.130 |
|
chronic hypertension |
2.60 |
1.799 |
0.587 |
|
previous urinary tract infection |
1.38 |
1.107 |
0.101 |
|
renal disease |
2.38 |
2.115 |
0.749 |
|
psychiatric hospitalization |
2.41 |
1.380 |
0.322 |
|
cigarette abuse |
1.78 |
1.374 |
0.318 |
|
marijuana abuse |
3.30 |
2.072 |
0.728 |
|
narcotic abuse |
5.58 |
1.905 |
0.645 |
from Table 2, page 342
|
Current
Gestation (Developing) Factor |
Univariate Odds
Ratio |
Logistic Odds
Ratio |
Regression
Coefficient |
|
size-date discrepancy |
1.46 |
1.393 |
0.331 |
|
severe anemia |
2.51 |
2.165 |
0.772 |
|
threatened abortion |
4.30 |
4.134 |
1.420 |
|
incompetent cervix |
24.34 |
12.527 |
2.528 |
|
surgery requiring hospitalization |
2.20 |
1.900 |
0.642 |
|
multiple gestation |
9.44 |
6.755 |
1.190 |
|
pre-eclampsia, mild |
2.37 |
1.705 |
0.534 |
|
bleeding after 20 weeks |
5.89 |
5.321 |
1.672 |
from Table 2, page 342
logistic score =
= SUM(regression coefficients for historic factors present) +
SUM(regression coefficients for developing factors present) + (constant )
where:
• constant = -3.193
number of risk factors =
= SUM(individual risk factors present)
Interpretation:
• minimum
score: -3.193
• logistic
score cutoff: -2.875. If the score is > -2.875, then the woman is at risk for
preterm delivery.
• The
number of risk factors present is associated with increased risk of preterm
delivery, with the risk increasing as the number of risk factors increase.
Individual risk factors:
• 4 of the
factors are not associated with high risk by themselves: history of previous
induced abortion, cigarette use, previous urinary tract infection, and previous
neonatal death. The presence of 2 or more of these factors places the person at
high risk.
• The
presence of any one of the remaining 18 factors indicates that the person is at
high risk.
Performance:
• 89% of
women delivering at <= 28 weeks of gestation were identified
• 79% of
women delivering at <= 32 weeks gestation were identified
• only
about 56% of women delivering at <= 37 weeks gestation were identified
•
Performance better for multipara and multigravid women.
•
Specificity improved as the number of risk factors increased, but the
sensitivity decreased.
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