Moore et al developed discriminant equations in 1984 that can be used to predict the risk of nephrotoxicity in patients treated with aminoglycosides. The authors were from the Johns Hopkins Hospital in Baltimore.
Aminoglycosides available at the time of the study: gentamicin and tobramycin
Nephrotoxicity was defined as a decrease in creatinine clearance by 50% or more.
|
Factors Known Prior to Starting Aminoglycoside Therapy |
Finding |
Points |
|---|---|---|
|
age in years |
|
(age in years) |
|
liver disease |
absent |
0 |
|
|
present |
1 |
|
initial creatinine clearance in mL/min |
|
(mL/min) |
|
sex |
male |
0 |
|
|
female |
1 |
after Table 2, page 354
discriminant score prior to therapy =
= (0.049 * (age in years)) + (1.872 * (points for liver disease)) + (0.025 * (points for creatinine clearance))+ (1.102 * (points for sex)) – 5.098
where:
• I did not see where the discriminant score based on pretreatment data was used to predict nephrotoxicity.
|
Factors Known by 72 Hours of Therapy with Aminoglycosides |
Finding |
Points |
|---|---|---|
|
initial 1 hour post-dose level (peak) in µg/mL |
|
(level in µg/mL) |
|
liver disease |
absent |
0 |
|
|
present |
1 |
|
age in years |
|
(age in years) |
|
initial creatinine clearance in mL/min |
|
(mL/min) |
|
sex |
male |
0 |
|
|
female |
1 |
|
shock |
absent |
0 |
|
|
present |
1 |
after Table 2, page 354
discriminant score for 72 hours =
= (0.333 * (drug level points)) + (1.312 * (liver points)) + (0.032 * (age in years)) + (0.016 * (points for creatinine clearance)) + (0.739 * (points for sex)) + (0.897 * (points for shock)) – 5.357
where:
• I would think this data would be known sooner than 72 hours after therapy was started. It may be that drug assays had a longer turnaround time in 1984, especially if microbial growth inhibition assays were used.
|
Discriminant Score at 72 Hours |
Risk of Nephrotoxicity |
|---|---|
|
< -2.0 |
< 0.8% |
|
-2.0 |
0.8% |
|
-1.5 |
1.2% |
|
-1.0 |
2.7% |
|
-0.5 |
5.8% |
|
0 |
11.2% |
|
0.5 |
21.5% |
|
1.0 |
33.5% |
|
1.5 |
51.5% |
|
2.0 |
65.3% |
|
2.5 |
77.7% |
|
3.0 |
85.4% |
|
3.5 |
91.5% |
|
4.0 |
95.4% |
|
> 4.0 |
> 95.5% |
after Figure 1, page 355
If this data is analyzed in JMP, the following equations can be derived:
risk over range of –2.0 to 0.5 =
= (1.562963 * ((score)^3)) + (8.1666667 * ((score)^2)) + (15.444974 * (score)) + 11.45873
risk over range of 0.5 to 1.5 =
= (12 * ((score)^2)) + (6 * (score)) + 15.5
risk over range of 1.5 to 4.0 =
= (0.3925926 * ((score)^3)) - (8.574603 * ((score)^2)) + (55.232011 * (score)) – 13.51667
A nomogram for calculating the risk is shown in Figure 3 on page 356,
Limitations:
• The data does not apply to patients treated with amikacin or netilimicin.
• The risk for nephrotoxicity increases with the creatinine clearance. I would have thought the reverse would be true.
Purpose: To predict nephrotoxicity in a patient treated with aminoglycosides using the discriminant equations of Moore et al.
Specialty: Nephrology, Clinical Laboratory, Pharmacology, clinical
Objective: risk factors
ICD-10: Y40.5,
