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Description

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.

 


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