Pine et al developed a discriminant function (DF) score for predicting outcome in patients with intra-abdominal infection requiring surgery. The score uses clinical data available prior to surgery. The authors are from the University of Washington in Seattle.
Parameters used for score:
(1) shock at any time: defined as clinical reduction in peripheral perfusion and 2 or more of the following:
(1a) systolic blood pressure <= 80 mm Hg for 1 hour;
(1b) pulse > 120 beats per minute with sinus rhythm for 1 hour;
(1c) urine output < 80 mL in 4 hours;
(1d) need for vasopressors to maintain blood pressure for 1 hours.(2) alcohol abuse
(3) age
(4) intestinal infarction
Additional factors impacting survival:
(5) malnutrition
(6) organ failure after surgery
Parameter |
Finding |
Points |
shock |
absent |
0 |
|
present |
1 |
alcohol abuse |
absent |
0 |
|
present |
1 |
age |
age <= 65 years |
0 |
|
age > 65 years |
1 |
intestinal infarction |
absent |
0 |
|
present |
1 |
discriminant function =
= (2.7 * (points for shock)) + (1.7 * (points for alcohol abuse)) + (1.6 * (points for age)) + (1.4 * (points for intestinal infarction)) – 1.3
Interpretation:
• minimum score: -1.3 (no risk conditions present)
• maximum score: 6.1 (all risk conditions present; in reality scores above 4 infrequent)
• The lower the score the greater the survival.
• Using the probability curve in Figure 4 (page 247) the point of 50% survival in a score of 0.75.
• Whether the probability curve is applicable may be debatable based on the bar graph data in Figure 4. But a score < 0.75 seems to show good survival, while a score >= 2.0 has a poor prognosis.
Discriminant Function |
Probability of Survival |
-1.25/-1.3 |
100% |
-1.0 |
99% |
-0.75 |
97% |
-0.50 |
95% |
-0.25 |
91% |
0 |
85% |
0.25 |
75% |
0.5 |
65% |
0.75 |
50% |
1.0 |
35% |
1.25 |
25% |
1.5 |
15% |
1.75 |
9% |
2.0 |
5% |
2.25 |
3% |
2.5 |
1% |
2.75/2.8 |
0% |
from curve shown in Figure 4, page 247
To generate the probability curve
probability of survival =
= 1 / (1 + EXP((-1) * X))
trial and error shows that
X =
= (-2.313 * (DF score)) + 1.7346
gives a reasonable approximation in the data in the table and the survival curve.
Performance:
• In the 106 patients studied, the score identified outcome in 92% of cases.
Limitations:
• Newer diagnostic techniques and therapies should have improved the prognosis since when the study was performed in 1983.
Specialty: Infectious Diseases, Surgery, general, Gastroenterology
ICD-10: ,