Noninvasive methods of detecting fetal anaemia: a systematic review and meta-analysis

Objectives  To estimate in a systematic review of the literature the diagnostic value of ultrasound and Doppler blood flow velocity in the evaluation of fetal anaemia.
Study selection and data extraction  Literature from 2000 to 2008 was identified using MEDLINE and EMBASE, the Cochrane Library and relevant specialist register of the Cochrane Collaboration, and by checking reference lists of known primary studies and review articles. Studies were selected if the accuracy of the fetal ultrasound parameters or Doppler studies of blood flow in the fetal vessels was estimated compared with a reference standard. Data from the selected studies were abstracted as 2 × 2 tables comparing the diagnostic test result with the reference standard. Results were pooled where appropriate. Diagnostic accuracy was expressed as likelihood ratios.
Results  Twenty-five primary studies were identified containing suitable data on middle cerebral artery Doppler peak systolic velocity (MCA-PSV). The largest group of studies whose data could be pooled containing nine studies gave a positive likelihood ratio of 4.30 (95% CI: 2.50 to 7.41) and a negative likelihood ratio of 0.30 (95% CI: 0.13 to 0.69) for 675 cases in detecting severe anaemia in the analysis.
Discussion  Although middle cerebral artery peak systolic velocity Doppler has limited diagnostic accuracy, it remains the gold standard for noninvasive screening of fetal anaemia.