Proudfoot et al evaluated the prognostic significance of plasma paraquat levels over time following ingestion. They developed a predictive line which separated probable nonsurvivors (above the line) from probable survivors (below the line).
Time in Hours After Ingestion
Plasma Levels in mg/L
4
2.0
6
0.6
10
0.3
16
0.16
24
0.10
If this data is analyzed in JMP the following lines can be estimated:
plasma concentration along predictive line over time interval =
= (A * (hours since ingestion)^3)) + (B * (hours since ingestion)^2)) + (C * (hours since ingestion) + D
Interval
(hour)^3
(hour)^2
(hour)
constant D
4 - 6
0
0.1041667
-1.741667
7.3
6 - 10
-0.000224
0.0123413
-0.228516
1.575238
10 - 24
0
0.001131
-0.052738
0.7142857
Interpretation:
• A patient with a plasma level greater than the plasma concentration on the line is at risk for death.
• A patient with a plasma level less than the plasma concentration on the line will probably survive.
• A person precisely on the line would be indeterminate.
Limitations:
• The line was described in 1979. Survival is probably better today due to better critical care management. However, it can help separate patients into low and high risk groups.
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