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Table 1 Characteristics of the diagnostic accuracy studies

From: High-throughput, non-invasive prenatal testing for fetal rhesus D status in RhD-negative women: a systematic review and meta-analysis

Study (First author/year) Location DNA extraction tool Exons targeted Controls Reference standard Gestational age at time of NIPT (median/range) Sample sizeα Confirmed RhD positive Confirmed RhD negative Inconclusive test results (%) Reasons for inconclusive results (n of cases)
Akolekar 2011 [19] UK (London) MDx BioRobot (Qiagen) 5 and 7 RhD+, RhD–, RHDΨ +, No DNA “Serologically at delivery” 12.4 (11–14) 586 410 176 84 (14.3) Maternal or fetal RHD variant and insufficient maternal plasma for further analysis (NR)!
Banch Clausen 2014 [6] Denmark QIAsymphony SP; MagNA Pure LC; MagNA Pure Compact Instrument (Roche) 5 and 10, or 5 and 7, or 7 and 10 RhD+, RhD–£ Cord blood serology~ 25 (23–28) 12,668 7830 4838 274 (2.2) Maternal weak D (93); maternal silent RHD variant (38); high level of maternal background DNA (29); technical problems (19); maternal DVI (14); weak PCR signal (13); suspected maternal RHD positive (3); no reported cause (65)
Chitty 2014 [16] UK (Bristol) MDx BioRobot (Qiagen) 5 and 7 RhD+, RhD–, RHDΨ+, No DNA Cord blood serology 19 (5–35) 4913 2890 2023 393 (8.0) NR
Finning 2008 [17] UK (Bristol) MDx BioRobot (Qiagen) 5 and 7 RhD+, RhD–, RHDΨ+, No DNA Cord blood serology> 28 (8–38) 1869 1156 713 56 (3.0) Insufficient DNA (30); suspected maternal RHD gene (25); failure to extract DNA from plasma (1)
Grande 2013 [25] Spain COBAS AmpliPrep (Roche) 5 and 7, 10$ RhD+, RhD– Cord blood serology 24–26 282 186 96 NR NR
Soothill 2015 [18] UK (Bristol) MDx BioRobot (Qiagen) 5 and 7 RhD+, RhD–, RHDΨ+, No DNA Cord blood serology 15–17 (mostly) 499* 315 184 61 (12.2) NR
Thurik 2015 [7] Netherlands MagNa Pure 96 (Roche) 5 and 7 RhD+, RhD– Cord blood serology^ 26 18383* 11,283 7100 NR NR
Wikman 2012 [20] Sweden MagNA Pure LC (Roche) 4 GAPDH Serology from cord blood or citrate samples from newborns+ 8–40 3291# 2073 1218 32 (1.0) RHD variant (14); no second sample (18, of which 13 were spontaneous abortions and miscarriages)
  1. αNumber of blood samples unless otherwise specified; * number of participants; # excludes pre-8 weeks gestation pregnancies; $ on 2nd DNA extraction, only to confirm RHD-negative results; £ Multiple controls without template were also included using sterile H2O; ! 5 mothers with insufficient DNA were excluded from the analyses and not classed as inconclusive
  2. NR: not reported; RhD+: RhD positive; RhD−: RhD negative; PCR: Polymerase chain reaction; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; ~ Region 1: ID-Card DiaClon ABD-Confirmation for donors, (DiaMed GmbH 1785 Cressier FR Switzerland) with monoclonal anti-D (cell lines ESD-1M, 175–2) that detects most weak RhD types and partial DVI phenotype; Region 2: direct agglutination in a gel matrix test with IgM monoclonal anti-D clone 175–2 (DiaMed); further tests in gel matrix test with in-house Dw1 anti-D for initial negative tests. For discrepancies, DNA extracted from the cord blood and tested for RHD exon 10 and further analyzed by PCR-SSP using the RH-type kit (Biologische Analysensystem GmbH, Lich, Germany); Region 3: Direct agglutination with monoclonal antibody Diagast anti-D IgM (ref. no. 71000) for RHD positive. For unexpectedly negative reactions, an additional IAT with anti-D IgG LOR17 was performed. IAT with anti-D IgG LOR17 was used for RHD negative; Region 4: Serological testing of cord blood RBC was done by using Seraclone Anti-D (RH1) Blend; Ref 802032 (Biotest, Germany); Region 5: Serological testing of cord blood RBC with 2 complete anti-Ds (Medion Diagnostics, IgM anti-D[MS201] and Seraclone, [Rh1] 226) in saline. For reactions of less than 3+ for both reagents, further investigation for D expression by IAT with two IgG anti-Ds. > No DNA extraction of cord blood samples. ^ Cord blood serology with WA-Diana system (DiaMed GmbH) using two monoclonal anti-D reagents, LHM 59/20 (LDM3) + 175–2 and ESD- 1M+ 175–2. Maternal and fetal RHD variant genes were analyzed with an RHD-multiplex ligation-dependent probe amplification (MLPA) assay on genomic DNA. Mutation analysis and copy number variation investigated via RHD MLPA. Discordant positive results due to maternal or fetal RHD variants were identified and excluded from the study. Samples with weak PCR signals were excluded. The Kleihauer–Betke test and multiplex short tandem repeat (STR)-PCRs on 15 systems on leukocyte-derived DNA were used exclude errors around cord blood collection. + Blood typing using DiaClon ABO/Rh for Newborns DVI+ gelcards