A multi-quarter assessment of sample rejection and cold chain deviations in Lassa fever surveillance in Nigeria, 2024–2025
Bibliographic record
Abstract
Introduction Lassa fever, a severe viral disease endemic to Nigeria, poses ongoing public health threats, with rapid diagnosis essential for outbreak control. Rising sample rejection rates and unstable logistical temperatures upon sample arrival at the National Reference Laboratory (NRL) compromise diagnostic accuracy. This study examines rejection trends and causes, identifies states with the highest rejection rates, and assesses regional and seasonal temperature deviations from the First Quarter, Second Quarter, Third Quarter, and Fourth Quarter of 2024 to the First Quarter of 2025. Findings aim to guide improvements in sample handling and surveillance logistics. Methods This retrospective study analysed 1,929 Lassa fever samples received at the NRL. utilizing Epi Info for descriptive statistics to assess rejection rates, transport temperatures, and trends across states and quarter. Results he overall rejection rate was 0.73%, rising from 0.28% in Q1 2024 to 4.08% in Q4 2024, before declining to 2.28% in Q1 2025. No rejections occurred in Q2 2024. Kogi and Ondo had the highest rejection proportions (17.65% each), while Benue, contributing over half of the total samples, accounted for 11.76% of rejections. Predominant causes of rejection were Case Investigation Form (CIF) without samples and sample spillage (35.29% each), followed by mismatched information and missing CIFs (11.76% each), and improper packaging (5.88%). Mean reception temperature was 17.68°C, above the World Health Organization’s recommended 2–8°C. The Second Quarter had the highest mean (18.74°C), and the Third Quarter the lowest (15.58°C). Zamfara recorded optimal cold chain conditions (3.2°C), while coastal states such as Rivers and Akwa Ibom recorded elevated rainy season temperatures. Conclusion The study reveals that although overall rejection rates were low, temperature instability and documentation gaps significantly compromised sample quality. It emphasizes the impact of these factors on diagnostic reliability and recommends addressing data completeness and transport time to improve outbreak response.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.003 | 0.004 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".