OECD 425

Question 1

It provides a more efficient use of animals and increases accuracy in predicting LD50

Answer 1

Half-log spacing

Question 2

Because the method has a bias towards starting dose, it is essential that initial dosing occur _____ the estimated LD50

Answer 2

Below

Question 3

To correct for the LARGE STATISTICAL ERROR what is included in the main test

Answer 3

Stopping rule keyed to properties of the estimate

Question 4

Easiest to apply to material that

Not be practical to use when

Answer 4

Produce death within one or two days

Delayed death (5 or more days) can be expected

Question 5

Used to facilitate animal-by-animal calculations that establish testing sequences and provide final estimates

Answer 5

Computers

Question 6

Used efficiently to identify chemicals that are likely to have low toxicity

Answer 6

Limit test

Question 7

The selection of a _____ increases the statistical power and made to INTENTIONALLY BIAS the procedure towards rejection of limit test

Answer 7

Sequential test

Question 8

The probability of correctly clarifying a compound will _____ as the actual LD50 more nearly resembles the limit dose

Answer 8

Decrease

Question 9

It is where animals are dosed, one at a time, at a minimum of _____ hour interval

Answer 9

Single ordered dose progression

48

Question 10

A combination of _____ used to keep the number of animals LOW while adjusting the dosing pattern to reduce the effect of a or starting value of low slope

Answer 10

Stopping criteria

Question 11

The LD50 is calculated using the

Answer 11

Method of maximum likelihood

Question 12

The results of the main test procedure serve as the

Answer 12

Starting point

Question 13

Intervals are determined by

Answer 13

Onset
Duration
Severity of toxic signs

Question 14

Antilog of 1 or estimated slope of the dose-response curve and should remain CONSTANT

Answer 14

Dose progression

Question 15

If animal tolerances are expected to be HIGHLY VARIABLE, consideration should be given to INCREASING the dose progression factor beyond the default _____

Answer 15

0.5

Question 16

The testing stops when one of the stopping criteria is met

Answer 16

3 consecutive animal survive at the upper bound
5 reversals occur in any 6 consecutive animal
At least 4 have followed the first reversal

Question 17

Stopping rule will be satisfied with _____ animals after test reversal

Answer 17

4-6

Question 18

Maximum likelihood calculation is performed using either

Answer 18

SAS or BMDP computer program packages

Question 19

The likelihood stopping-ratio stopping rule is based on _____ measures of test progress

Answer 19

3

Question 20

Comparisons are made after each animal tested after the _____ that does not already satisfy the 1st and 2nd criterion

Answer 20

6th

Question 21

Comparisons are most really performed in an _____ and can be executed _____

Answer 21

Automated manner
Repeatedly ex. Spreadsheet routine

Question 22

Any of the confidence intervals provides valuable information on the _____ of the main test conducted.

Answer 22

Reliability and utility

Question 23

MORE uncertainty associated with the estimated LD50
Reliability is LOW
Usefulness may be MARGINAL

Answer 23

Wide confidence interval

Question 24

LITTLE uncertainty associated with the estimated LD50
Reliability is HIGH
Usefulness is GOOD

Answer 24

Narrow confidence interval

Question 25

At least three different size have been tested and the MIDDLE DOSE has at least one survival and one death

The actual level of confidence is _____

Answer 25

Profile-likelihood based computational procedure

Not exact

Question 26

Improve the ability of the test overall to respond to varying underlying conditions

Answer 26

Random stopping rule

Question 27

Approximate interval

Answer 27

Only occur when dose response is steep
True LD50 is expected to be contained within the calculated interval
Relatively narrow and sufficiently accurate

Question 28

Method permits estimation of LD50 with a

Answer 28

Confidence interval