Timing of blood extraction in epidemiologic and proteomic studies: results and proposals from the PANKRAS II Study

Abstract

There are no consensus guidelines or standards for epidemiologic and '-omics' studies using blood biomarkers on how to report the timing of extraction of blood samples. However, disease-induced changes in blood concentrations of exogenous and endogenous compounds may bias studies. The aim of the present report is to describe the timing of blood collection with respect to a variety of relevant clinical events in the PANKRAS II Study, and to suggest ways to display graphically the quantitative information. Subjects were 167 incident cases of exocrine pancreatic cancer prospectively recruited in five teaching hospitals in eastern Spain. Over 80% of patients had blood extracted during the first 6 months since onset of cancer symptoms, and 82% within the first month of admission to a study hospital. Over 80% of cases had blood drawn after an ultrasound, a CT scan or an ERCP, 25% after a laparotomy, and 37% after treatment onset. All three intervals from blood extraction to diagnosis, to treatment onset and to interview had a median of 0 days, and 88% of cases had blood drawn within 2 weeks of diagnosis. Over 72% of cases had concentrations of total lipids in the medium, normal range. Results suggest ways to report intervals involving blood biomarkers and may contribute to develop consensus guidelines and standards on the collection of blood samples in epidemiologic and '-omics' research.

Influence of tumor stage, symptoms, and time of blood draw on serum concentrations of organochlorine compounds in exocrine pancreatic cancer

“…Methods of the PANKRAS II study have been described in detail [10,18,[32][33][34][35][36][37][38][39][40]. Briefly, subject recruitment took place between 1992 and 1995 at five general hospitals in the Mediterranean part of Spain, where 185 incident cases of exocrine pancreatic cancer (EPC) were prospectively identified.…”

“…Patients were interviewed face-to-face by trained monitors during hospital stay, close to the time of diagnosis [36]. The respondent was the patient himself in 93% of the cases and a relative alone in 7%.…”

“…Blood was drawn from cubital veins following the standard procedures of participating hospitals; largely, in the early morning and with patients fasting [36,38,40]. We had one measure of serum concentrations of organochlorines per subject.…”

“…The median time between the first symptom of cancer and blood extraction (IES) was 74 days; between hospital admission and blood extraction, 15 days; between diagnosis and blood extraction, 1 day; and between treatment onset and blood extraction, 0 days [36,38]. Of the 34 patients who started treatment before blood extraction, 30 underwent only surgery, 3 received only chemotherapy, and 1 received only treatment for pain [36]. Each interval was examined to obtain the fewest categories needed to retain the underlying interrelationships and to maximize the stability of the estimates.…”

“…Total cholesterol and triglycerides levels were determined enzymatically (CHOD-PAP and GPO-PAP methods respectively) [36,38,39] using serum obtained at the same time than for organochlorine analyses. Total serum lipids were calculated from total cholesterol and triglycerides using the standard formula 2 of Phillips et al [42,43], and organochlorine concentrations were hence individually corrected for total serum lipids (TSL) [10,[34][35][36][37][38].…”