Prilično sam sigurna da je to to, samo možda treba promeniti formulaciju, u zavisnosti od toga kako su kod Vas nazvane grupe (kontrolna, placebo, tretirana...).
Web reference koje sam ostavila objašnjavaju pojmove 'drop in' i 'drop out'.
Prva referenca:
Noncompliance rates
The noncompliance (or crossover) rates are specified by the drop-out rate (from treatment group to control group) and drop-in rate (from the control group to treatment group). The specification of the drop-out rate is similar to that of the drop-in rate. It assumes that crossovers can only occur at specified time points.
(a) To specify the drop-in rate, the user first specifies the number of time point(s) at which drop-in occurs. This number, K, is an integer ranging from 1 to 20.
(b) The user then inputs the K time-points at which drop-in occurs, separated by blank spaces and in increasing order of magnitude.
(c) This is followed by inputting the drop-in rates at these times. The drop-in rate, which is the proportion of subjects that switch from the control group to the treatment group, is a number between 0 and 1.

Druga referenca:
Another assumption was that the rate of nonadherence to the study treatment would be 14 percent and that 5 percent of the men in the placebo group would end up taking finasteride (the drop-in rate). Serum dihydrotestosterone was measured in a randomly selected 5 percent sample of men as a marker of adherence to study medication in the finasteride group and as a measure of the drop-in rate in the placebo group.

What they are talking about here is men who, for whatever reason, ended up taking the study drug outside of the study. Finasteride, aside from its prostate cancer effects (which obviously weren't well-established at the time of this study), is used for hair loss and BPH. Quite wisely, the investigators predicted this (the "drop-in") and randomly sampled blood from both the treatment and placebo arms of the study. Again, this is what you do in a well-funded study.
Što se tiče srpskih referenci, uspela sam da pronađem samo primere za 'drop out':
Srednja doza venlafaksina ER je bila 221.5 mg/dne što znači da su neki bolesnici dobivali i veće doze od 225 mg/dne što je maksimalna doza preporučena od strane FDA u poremećajima u kojima ovaj lijek ima indikaciju (depresivni poremećaj, generalizirani anksiozni poremećaj, socijalna fobija i panični poremećaj). Stopa ispadanja iz studije je bila podjednaka u obje grupe. Najčešće prijavljena nuspojava u obje grupe je bila glavobolja. 15 bolesnika je imalo nuspojave zbog kojih je prekinuto uzimanje venlafaksina ER, dok je takvih bilo 9 u placebo grupi. Najčešće su se tužili na mučninu ili omaglicu.