3,257 visits, and the patients were never the constraint

Abstract

Background: The sponsor — a top-tier global diagnostics manufacturer¹ — commissioned a high-throughput healthy-female serial-draw specimen collection program to support immunoassay verification work on cycle-tracked analytes. The program required serial sampling from each enrolled subject across the menstrual cycle, with subject inclusion criteria anchored on a regular cycle, no current pregnancy, and no exogenous hormonal therapy. Throughput requirements at the program level — thousands of subject-visits across a five-month enrollment window — placed the binding operational constraint on per-site coordinator capacity rather than on subject pool availability.
Methods: RDI executed the program as full-service CRO from the same Van Nuys operational spine that runs the rest of this engagement series. Eight sites were activated, anchored by two high-density women’s-health clinics carrying the bulk of program volume, supplemented by a six-site network for case-mix and geographic diversity. The protocol structured the visit cadence around the subject’s reported cycle; sites scheduled visits forward from the first contact date to capture the protocol-defined visit windows. Specimen handling and processing ran centrally at the RDI reference laboratory.
Results: Cumulative visit count crossed 123 by end-November 2025, 1,049 by end-December, 2,408 by end-January 2026, 3,109 by end-February, and reached 3,257 at end-March 2026 (Fig. 1). The two lead sites carried 64% of program volume between them: Site A (1,454 visits) and Site B (625 visits). The 6-site supplementary network distributed the remaining 36% with the third site (Site C, 572 visits) running at near-lead-site cadence and the long-tail sites contributing under 130 visits each (Table 1; Fig. 2). January 2026 monthly throughput of 1,359 subject-visits is approximately 7× the average monthly cadence across the rest of the engagement series.
Conclusions: Throughput at this scale is operationally a coordinator-capacity problem rather than a subject-pool problem. The lead-site model — two clinics with deep women’s-health patient panels and pre-existing high-throughput coordinator infrastructure — produced the bulk of program volume with marginal contribution from the supplementary network. The same two-lead-site shape transfers to other high-throughput specimen-bank programs.

Keywords: in vitro diagnostics; women’s health; serial-draw; menstrual cycle; specimen banking; high-throughput specimen collection; reference range establishment.

1. Background

The sponsor commissioned a high-throughput specimen collection program to support immunoassay verification work on cycle-tracked analytes in healthy adult females. Verification across analytes that vary systematically with the menstrual cycle requires a substantial pool of cycle-characterised specimens; the program target placed the program in the highest-throughput tier of the engagement series, with thousands of subject-visits required across the available enrollment window.²

The program is operationally distinct from the lower-volume specimen collection programs reported elsewhere in this series. The binding constraint shifts from subject-pool access (the principal constraint in hard-to-reach-population programs) and from cohort-target attainment (the principal constraint in mass-spec multi-cohort programs) to per-site coordinator capacity. A site that can run 200 subject-visits per month is operationally ten times more useful than two sites that can run 20 visits each per month.

2. Constraints encountered

Three constraints shaped the execution plan:

Coordinator capacity is the binding constraint

At the program throughput required, per-site coordinator capacity sets the ceiling on weekly subject-visit count. A site with one full-time coordinator running healthy-volunteer visits at typical pace delivers ~80–120 visits per month; a site with multiple coordinators and high-throughput visit infrastructure delivers two to three times that. Site selection had to weight coordinator-capacity disclosure equally with subject-pool disclosure, and SIV training had to drill on visit-flow efficiency at coordinator level.
Cycle timing dictates visit scheduling

The serial-draw cadence is anchored on the subject’s self-reported cycle date; sites schedule visits forward from the first contact date to capture the protocol-defined visit windows around the cycle. Subject reschedules and missed visits cascade into protocol deviations if not caught at the coordinator level; sites with lighter coordinator coverage drop visits at the cycle-window boundary.
Specimen-handling throughput at the central lab

1,000-plus visits per month places real throughput pressure on the central reference lab’s specimen-handling pipeline: receipt logging, processing, aliquoting, freezer-bank inventory. Specimen-handling SOPs were tightened ahead of the December–January peak; receiving-bench staffing was increased for the peak window; freezer-bank capacity was confirmed in advance against the program’s storage-volume forecast.

Peak monthly throughput of 1,359 visits in January 2026 is approximately 7× the typical monthly cadence across the rest of this engagement series. The lab’s receiving bench, processing pipeline, and freezer-bank inventory all had to scale alongside the site network.

3. Methods

RDI executed the program as full-service CRO. Three operational moves are reported here in order of implementation.

3.1. Two-lead-site model with high-throughput coordinator infrastructure

Site A (1,454 visits across the enrollment window) and Site B (625 visits) were activated as the program lead sites. Both sites had pre-existing high-throughput women’s-health coordinator infrastructure — multiple coordinators, established visit-flow templates, large electronic-scheduling capacity. Site selection prioritised coordinator capacity over patient-panel-size disclosure: a site with a smaller patient panel and a stronger coordinator team delivered more visits per month than a site with a larger panel and weaker coordinator coverage.

3.2. Six-site supplementary network for case-mix and geography

Six additional sites were activated as the supplementary network — Site C (572 visits, running at near-lead-site cadence), Site D (267 visits), Sites E–H (combined 339 visits across the long tail). The supplementary network served two purposes: case-mix diversity beyond the lead sites’ patient demographics, and contingency capacity in the event a lead site faltered through the peak window.

3.3. Specimen-handling pipeline scaled in advance of peak

Receiving-bench staffing was increased and freezer-bank capacity was confirmed ahead of the December–January peak. Specimen-handling SOPs were tightened to compress the receipt-to-processing window at scale; receiving-bench protocols were reviewed against the forecast specimen volume in mid-November 2025. The lab’s ability to absorb 1,359 visits in a single month without specimen-handling drift was validated through the peak.

Distributed-network model (alternative)

15–20 sites with moderate coordinator capacity each, distributed across regions. Per-site visit volume 60–80 per month. Total program throughput: 900–1,500 visits/month. SIV cycle: 15–20 site-initiation visits + per-site training; high coordination cost.

Two-lead-site model (this program)

2 lead sites at 200–400 visits/month + 6-site supplementary network. Total program throughput: 600–1,400 visits/month. SIV cycle: 8 site-initiation visits + concentrated coordinator training at the lead sites; lower coordination cost per visit delivered.

4. Results

Cumulative visit count crossed 123 by end-November 2025, 1,049 by end-December 2025, 2,408 by end-January 2026, 3,109 by end-February 2026, and reached 3,257 at end-March 2026 (Fig. 1). Monthly cadence ramped sharply through November and December as the lead sites came up to full coordinator capacity, peaked at 1,359 visits in January 2026, then unwound through February (701) and March (148) as cycle-window draws closed out for early-enrolled subjects.

Site distribution at end-March 2026: Site A 1,454 visits (45%), Site B 625 visits (19%), Site C 572 visits (18%), Site D 267 visits (8%), Site E 125, Site F 107, Site G 76, Site H 30 visits (Table 1; Fig. 2). The top-three-site share is approximately 81% of program volume; the long-tail four sites (E–H) combined contributed under 350 visits across the program.

Nov 2025 First SIVs / +123

Dec 2025 +926 / month ramp

Jan 2026 +1,359 / month peak

Feb 2026 +701 / month tail

Mar 2026 Cycle closeout

Mar 2026 3,257 cumulative

Table 1 Visit count by site across the 5-month enrollment window. The two lead sites contributed 64% of program volume; the top three sites contributed ~81%; the long-tail four sites contributed under 350 visits combined.
Site	Setting	Visits	Share
Site A	High-density women’s-health clinic; multi-coordinator high-throughput infrastructure	1,454	45%
Site B	High-density women’s-health clinic; multi-coordinator infrastructure	625	19%
Lead-site subtotal	2 sites carrying the bulk of program volume	2,079	64%
Site C	Multi-specialty research center with women’s-health track	572	18%
Site D	Women’s-health clinic	267	8%
Site E	OB/GYN practice	125	4%
Site F	OB/GYN practice	107	3%
Site G	RDI internal validation site	76	2%
Site H	Multi-specialty research center	30	1%
Supplementary network subtotal	6 sites for case-mix and geography	1,177	36%
All sites at end-March 2026 reporting date	8 sites total	3,257	100%

Fig. 1 Cumulative visit count (orange line) and monthly visit count (gray bars) across the 5-month enrollment window. Monthly cadence ramped sharply through November and December as lead sites came up to full coordinator capacity, peaked at 1,359 visits in January 2026, then unwound through February and March as cycle-window draws closed out for early-enrolled subjects. Source: RDI Salesforce enrollment dashboard at end-March 2026.

Fig. 2 Visit count by site across the 5-month enrollment window. The two lead sites (orange-tan; Site A and Site B) carried 2,079 of 3,257 visits (~64%); the supplementary network (navy; Sites C–H) contributed the remaining 36% with most volume concentrated at Site C and Site D. The long-tail four sites (E–H) combined contributed under 350 visits. Source: RDI Salesforce enrollment dashboard at end-March 2026.

5. Discussion

Three observations bear noting. First, throughput at this scale is operationally a coordinator-capacity problem rather than a subject-pool problem. The eligible-subject pool for the program inclusion criteria runs into the millions in the U.S. adult population; the binding constraint is how fast a site can move subjects through screening, consent, scheduling, and the serial-draw cadence. A site with a smaller patient panel and a stronger coordinator team delivers more visits per month than a site with a larger panel and weaker coordinator coverage.

Second, the lead-site model is operationally cheaper per visit delivered than a distributed-network alternative. Two lead sites + a six-site supplementary network produced 3,257 visits in 5 months with 8 SIVs and concentrated coordinator training; the same volume run across 15–20 distributed sites would require 2–3× the SIV count and per-site monitoring overhead with no offsetting throughput benefit.

Third, the central reference-lab pipeline has to scale alongside the site network. The peak month of 1,359 visits placed real throughput pressure on receiving-bench staffing, processing pipeline capacity, and freezer-bank inventory. Specimen-handling SOPs were tightened ahead of the peak; receiving-bench staffing was increased; freezer-bank capacity was confirmed in advance against the program’s storage-volume forecast. The reference lab is part of the operational scale-up, not a downstream service.

6. Conclusion

High-throughput healthy-female serial-draw specimen collection is operationally a coordinator-capacity problem at the per-site level and a specimen-handling-throughput problem at the central reference lab. A two-lead-site model with a six-site supplementary network delivered 3,257 visits in 5 months, peaking at 1,359 visits in a single month at approximately 7× the typical monthly cadence across the rest of this engagement series. The same operational frame — coordinator-capacity-driven site selection, lead-site concentration, central-lab pipeline scaled in advance — transfers to other high-throughput specimen-bank programs.

Notes & References

Sponsor identity withheld per confidentiality terms. Specific protocol code, target counts, analyte names, and assay platform names omitted. Sponsor descriptor reflects the sponsor’s category.
Visit-count totals reported here reflect protocol-defined subject-visits across the serial-draw cadence; the underlying unique-subject count is smaller and is not separately reported in this operations report. Cycle characterisation, eligibility verification, and visit-window adherence are all per-subject metrics tracked at the protocol level and not reported here.
Comparative monthly-cadence figures (~7× typical engagement-series cadence) reference the median monthly enrollment cadence across the other six programs in this engagement series at their respective peaks.
Endpoint counts (3,257 visits across 8 sites at end-March 2026; +1,359 January peak; ~64% lead-site share) are taken from the RDI Salesforce enrollment dashboard.
Site labels in Table 1 and Fig. 2 are anonymised. Site descriptors reflect the site’s clinical setting category, not its specific institutional identity.
No human subjects data, identifiers, or laboratory results are reported. This is an operations report, not a clinical-results publication.