Ten blood draws per subject in five weeks, with the retention to finish
Top-tier global diagnostics manufacturer · serial-draw progesterone specimen bank · 60 subjects × 10 visits, ~575 specimens, one site, 2023
The challenge the client gave us
A top-tier diagnostics manufacturer needed serial-draw evidence for a progesterone assay across the menstrual cycle — not one sample per subject, but 10 visits per subject, at least 3 days apart, across a 5-week window, with both serum (SST) and lithium-heparin plasma collected every visit.
The catch: the subjects are healthy women 18–45 with regular 21–35 day cycles, both ovaries, no hormonal birth control in the last 60 days, and not pregnant — a narrow eligibility screen. And then each one has to come back ten times. The operational test isn't enrolling 60 women; it's keeping all 60 engaged through ten visits so the serial dataset doesn't collapse into dropouts.
At a glance
| Subjects | 60 (raised from 50 by a mid-study amendment) |
| Visits per subject | 10, ≥3 days apart across a 5-week window |
| Matrices per visit | 2 (serum SST + LiHep plasma) |
| Specimens delivered | ~575 |
| Architecture | Single site, run near its coordinator-throughput ceiling |
| Peak month | +376 specimens (May 2023) |
Timeline
- Mar 2023 Program signed; IRB sponsorship, site oversight, and GCP collection stood up
- Apr 2023 Site opens; program crosses ~99 specimens on a partial first month
- May 2023 Peak month — +376 specimens in a single calendar month
- Jun 2023 Planned pause for site staffing (a quiet month by design, not a stall)
- Jul 2023 Amendment 1 raises enrollment from 50 to 60 subjects mid-flight
- Aug 2023 Program closes at ~575 specimens — ~82% delivered in the first two months
What we did as a CRO
| CRO responsibility | What RDI did on this study |
|---|---|
| Regulatory & study start-up | Acted as IRB sponsor of record and stood up the protocol, consent, and a 7-year specimen archive |
| Site selection & feasibility | Chose a single fully-resourced site with multi-coordinator coverage and a standing healthy-adult-female panel large enough for the serial-draw cadence — a deliberate architecture call, not a default |
| Site activation & training | Activated one site running near its per-site coordinator-throughput ceiling instead of spreading volume thin across a network |
| Recruitment & enrollment | Screened healthy women 18–45 against the cycle/ovary/contraception/pregnancy criteria; structured subject reimbursement for retention ($50/visit plus a $75 final-visit completion payment) so all 10 visits actually happened |
| Kits, samples & lab | Collected serum + LiHep plasma each visit (1 × 10 mL each, ≥4 mL per tube), aliquoted to 1 mL, frozen at −20 °C within 24 hours; scaled the reference-lab receiving bench ahead of the peak month so +376 specimens in May didn't back up |
| Monitoring & data | Central monitoring and shipping oversight across the serial-draw window |
| Project management & close-out | Absorbed the mid-study expansion from 50 to 60 subjects without restarting, and closed the specimen bank on schedule |
What made it hard
- Retention is the whole study. Ten visits per subject over five weeks means a subject who quits at visit 6 doesn't leave a partial dataset — she leaves a hole in a serial curve.
- The eligibility screen is narrow. Regular cycles, both ovaries, no hormonal contraception for 60 days, not pregnant — a smaller qualified pool per screen.
- Two matrices, every visit. Serum and LiHep plasma at each of 10 visits, aliquoted and frozen on a tight cold-chain clock, multiplies the handling load.
- A single site concentrates risk. With no contingency network, the chosen site had to be right the first time.
- The peak month was enormous. +376 specimens in one calendar month is well above ordinary per-site cadence and put real pressure on the central reference-lab pipeline.
How we solved it
- We designed reimbursement as a retention instrument, not an afterthought — a per-visit payment plus a completion bonus that made finishing all ten visits the rational choice for subjects.
- We ran it through one fully-resourced site with multi-coordinator coverage and an existing healthy-female panel, so the serial cadence sat inside the site's real capacity.
- We scaled the reference lab ahead of the peak, confirming freezer capacity and staffing the receiving bench before May's +376 specimens arrived.
- We absorbed the 50-to-60 amendment in-flight, adding subjects without resetting the program.
The result
The program delivered ~575 specimens across 60 subjects and 10 visits each, with roughly 82% of volume in the first two months and a +376-specimen peak in May 2023 — sustained single-site coordinator throughput, retention held across a demanding serial protocol, and an in-flight scope expansion absorbed without a restart.
Source: RDI specimen-bank inventory at program close, August 2023. Sponsor identity withheld per confidentiality terms; single-site reference is operational architecture, not a marketing claim. Operations report, not a clinical-results publication.