How do I handle missing sections?

Problem

I have had several occasions where for one reason or another the section that I should use for counting is missing. What should I do in this case? Skip the section? Use another section? Any insight would be appreciated.

Solution

The important issue here is why the section cannot be used in counting. If the reason is random, then there are stereologically sound methods of using the samples despite the missing section. A dropped section, a section ruined during slicing, a section that did not stain properly are possible random causes. All that matters is that the section is not dismissed for preferential reasons. Such reasons might be that the section had very little of the region of interest on it, or the cells were too crowded to make counting easy. Removing a section for random reasons is similar to applying the fractionator principle. Suppose there are 6 sections. Roll a die and a number from 1 to 6 is chosen at random. Remove that section. Now the remaining 5 sections represent 5/6 of the original. Therefore, an unbiased estimate of the original quantity is the estimate from the 5 sections divided by the sampling fraction which is 5/6.

An important consideration is that although the result is unbiased, the variance has been increased.

If the sections are well spread out it is also possible to substitute a neighboring section. Suppose every 15th section is being used. If it is available, then use the 14th or 16th section as a substitute. Report this substitution in the results. This technique may be more difficult to justify if every other section is being used.

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