Antenatal monitoring of anti-D and anti-c: could titre scores determined by column agglutination technology replace continuous flow analyser quantification?

Evaluating automated titre score as an alternative to continuous flow analysis for the prediction of passive anti-D in pregnancy

OBJECTIVES

To evaluate the potential of the automated titre score (TS) as an alternative method to continuous flow analysis (CFA) for the prediction of the nature of anti-D in pregnancy.

BACKGROUND

The 2016 revised British Society for Haematology (BSH) antenatal guidelines recommended a measurement of anti-D concentration by CFA to ensure the detection of potential immune anti-D. Due to high referral costs and resource pressures, uptake has been challenging for hospital laboratories. Serious Hazards of transfusion (SHOT) data have previously shown that this has contributed to missed antenatal follow ups for women with immune anti-D and neonates affected by haemolytic disease of the fetus/newborn.

METHODS/MATERIALS

In this multicentre comparative study, samples referred for CFA quantification were also tested by an ORTHO VISION automated anti-D indirect antiglobulin test (IAT) serial dilution and then converted to TS. CFA results and history of anti-D prophylaxis were used to categorise samples as passive or immune, with the aim of determining a potential TS cut-off for CFA referral of at risk patients.

RESULTS

Five UK National Health Service (NHS) trusts generated a total of 196 anti-D TS results, of which 128 were classified as passive and 68 as immune. Diagnostic testing of CFA and TS values indicated a TS cut-off of 35 to assist in distinguishing the nature of anti-D. Using this cut-off, 175 (89%) results were correctly assigned into the passive or immune range, giving a specificity of 92.19% and a negative predictive value of 91.47%.

CONCLUSION

TS in conjunction with clinical and anti-D prophylaxis history can be used as a viable and cost-effective alternative to CFA in a hospital laboratory setting.