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Medium-term storage of frozen residual antenatal sera in gel separator tube is suitable for subsequent serological investigation of intrauterine infection
  1. Weiling Ng1,
  2. Ter Yong Tan1,
  3. Xin Yu Venessa Chow1,
  4. Siew Hoon Lim1,
  5. Wei Yee Wan1,2
  1. 1Microbiology, Singapore General Hospital, Singapore
  2. 2SingHealth DUKE-NUS Pathology Academic Clinical Programme, Singapore
  1. Correspondence to Dr Ter Yong Tan, Microbiology, Singapore General Hospital, 169608, Singapore; tanteryong87{at}


Aim We assessed the feasibility of storing sera in primary gel separator tube over medium-term for retrospective serological tests to facilitate investigation of intra-uterine infection.

Method 120 residual serum samples, consisting of 30 positive samples each for rubella, cytomegalovirus, parvovirus B19 and varicella zoster IgG were aliquoted into secondary propylene tubes and stored together with the original primary tubes at −20°C for 1 year. The serum was subsequently retested to compare results from both storage methods.

Results Haemolysis was observed in 49.2% of serum stored in the primary tubes. However, there was no difference in both the qualitative and quantitative results after storage of serum samples in either receptacle.

Conclusion Sera can be stored in primary blood tube for up to 1 year without affecting serological results. For laboratories with adequate freezer space to store samples in primary blood tubes, this would streamline workflow saving manpower and time, avoid mislabelling of aliquots, reduce consumable costs and prevent unnecessary biohazard exposures.

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  • Handling editor Patrick J Twomey.

  • Contributors *WYW, WN, XYVC and SHL designed and performed the experiments. TYT, WN and WYW analysed the results and wrote the manuscript. *Guarantor.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer-reviewed.