Bruinsma et al. BMC Public Health 2011, 11(Suppl 5):S7 http://www.biomedcentral.com/1471-2458/11/S5/S7 pack was sent. In other instances, an address was located for the parents but not the child. In this case we contacted the parents and asked them for contact details of their daughter(s) or requested that they forward to them our letter of invitation. Some parents were reticent or refused to do this as they felt it would raise issues they would rather let lie. In these instances we tried to collect limited data from the parents on their daughter’s health and relationship status. In all instances it is vital for rigorous epidemiological research that access to sources for tracing be main- tained. Privacy is important; however this must be balanced with the public expectation that information is available on the long-term impact and effects of medical treatments. Studies would be unable to be conducted, or the validity of which would be compromised, if access to named or identifying data on a population-based level was not possible. The issues outlined in the previous two sections, namely storage and retrieval of medical records, avail- ability of records and willingness of practitioners to par- ticipate, tracing and recruitment of participants, have ongoing implications for public health research. Each year new treatments and new medications are added to standard clinical practice, the long-term implications of which cannot always be foreseen [44]. An interesting example, with some parallels to the treatment of tall girls, is the current use of hormone treatments for short stature [45]. Another example is the potential need to trace women administered human pituitary growth hor- mone (hGH) [46] and human pituitary gonadotrophin [47]. Tracing plays an important part in accurately reporting outcomes and reducing bias in findings. It requires access to population-based identifying data sources or use of a unique identifying number. However, prior to this, accurate records of treatment must be kept. Practicalities of data collection The Tall Girls Study collected data on multiple health and psychosocial outcomes. This necessitated a range of quantitative and qualitative methods each of which had specific challenges. The primary exposure of interest was the synthetic oestrogens used to accelerate puberty and retard growth (height) which would be ascertained through access to medical record data. A postal ques- tionnaire collected self-reported information on current health status using standard validated tools, treatment history, family attitudes to tall stature, perceived advan- tages and disadvantages to tall stature and satisfaction with treatment using structured and open-ended ques- tions; and personal and demographic details including current height. Information considered more complex or sensitive including reproductive and sexual history Page 5 of 8 and mental health status was collected using a computer assisted telephone interview (CATI). While the majority of women participated in all components of the study, a small number of women chose to only participate in a component of the study. Postal questionnaires were mailed to women with the initial approach letter outlin- ing the study. Return of a completed questionnaire implied informed consent. Included with the postal questionnaire were two separate consent forms, one for permission to access their medical record for assessment and treatment details, and the second for permission to be contacted for a CATI interview. Due to the number of telephone interviews that needed to be conducted over a relatively short period of time and the difficulties in staffing and scheduling these, it was decided to contract these interviews to a com- mercial interviewing company. Once interviewing com- menced it became clear that the interviewers had very little experience in health, they did not tailor contact to the times that women had already indicated were conve- nient and although initially they had indicated that they were happy for the project manager to be on site and monitor some of the interviews, in practice this was not the case. The interviews were significantly more com- plex and took significantly longer than they had esti- mated in their costing (despite a number of briefings). The commercial company was not willing to address these issues and only completed half of the CATI interviews. The remaining interviews were conducted in-house by the project manager and two members of the project team. This change meant that any queries about the study or associated issues regarding being an assessed or treated tall girl could be clearly and accurately addressed. An additional advantage of the project team being involved in data collection was that it gave a good sense of the strengths and weaknesses of data items which then informed the analysis process. While con- ducting the interviews in-house had advantages, it also had costs (both economic and emotional). A small num- ber of CATIs needed to be conducted with women who were living overseas and it required rescheduling of staff work hours as a high proportion of interviews needed to be conducted between 5 and 9pm at night and in some instances in the early hours of the morning. Some of these interviews were also emotionally taxing and the three in-house interviewers conducted between 50-100 interviews each over the space of a few months. Regular debriefing was required; this was conducted by other team members. Analysis of one of the primary outcomes, fertility, col- lected by the CATI did not find any significant differ- ence in rates of reporting between the interviews conducted in-house or outsourced, which was reassuring