Systematic Review and Meta-Analysis of Congenital Toxoplasmosis Diagnosis: Advances and Challenges

Table 1

Major goals of selected articles.

Samples in the major goal^†				Analysis of performance	Diagnosis improvement	Comparisons	To distinguish acute and chronic phase of infection	Others	Year	Ref.
AF				To evaluate Se/Sp of a prenatal AF using PCR	—	To compare Se of PCR in AF according to intervals between amniocentesis and infection. To compare epidemiological parameters in children with positive and negative PCR results	—	To evaluate time of treatment and gestational age on CT diagnosis	2001	[5]
AF				—	To develop a duplex real-time PCR based on fluorescence resonance energy transfer to quantify parasite load and to determine assay sensitivity	To compare routine PCR and the lightcycler PCR	—	To correlate parasite load to ultrasonographic abnormalities. To correlate parasite load to the gestational age at the time of maternal infection	2001	[6]
AF				To evaluate Se/Sp of PCR and bioassay on AF	To combine PCR with mice inoculation to improve sensitivity	To compare Se/Sp between PCR and mouse inoculation. To compare prenatal and postnatal diagnosis	—	—	2002	[7]
AF				—	—	To compare T. gondii detection limit of 4 PCR methods in AF (conventional PCR, fluorescent PCR, real-time qPCR with SYBRGreen or with fluorescence energy transfer hybridization probe)	—	—	2006	[8]
AF				—	—	To compare different PCR methods (primers for B1, rDNA, and AF146527)	—	—	2009	[9]
AF				—	—	To compare 3 PCR assays for T. gondii detection in AF (commercial nested PCR and two laboratory-developed PCRs: conventional and real time)	—	—	2012	[10]
AF				To evaluate performance (Se, Sp, PPV, NPV, PLR, NLR and EF) of PCR in AF	—	To compare performance of 4 PCR methods for CT diagnosis in AF: nested multiplex, conventional, and real time	—	—	2013	[11]
AF				—		To compare 3 PCR assays used for T. gondii infection diagnosis: P30-PCR, B1-PCR, and RE-PCR	—	To characterize the infecting T. gondii strains from the clinical specimen using B1 multicopy gene as target	2013	[12]
AF				To evaluate Se, Sp, PPV, NPV of PCR in AF to detect T. gondii infection	—	To compare Se of PCR performed at second or third trimester amniocentesis	—	To evaluate influence of treatment and timing of amniocenteses in PCR Se. To evaluate the outcome in infants with CT diagnosed by amniocenteses	2015	[13]
AF	BL			To evaluate Se/Sp of different diagnosis methods in AF and P-CB	To combine two diagnosis methods to improve diagnosis	To compare Se/Sp of different diagnosis methods	—	—	2002	[14]
AF	BL			—	To combine PCR with IgG avidity to improve CT diagnosis	—	—	—	2011	[15]
AF	BL			—	—	—	—	To characterize T. gondii present in AF and M-PB by genotyping	2012	[16]
AF	BL			—	—	—	—	To characterize atypical cases of T. gondii seroconversion (without IgM detection or with transient IgM levels) based on serology and PCR in AF	2013	[17]
AF	BL			To determine Se/Sp of diverse diagnosis methods and samples (AF, CB, and PB)	—	To compare prenatal and birth samples. To compare different PCR methodologies and different samples	—	—	2013	[18]
AF	BL			To verify the accuracy of the IgG avidity index to diagnose recent T. gondii infection	—	To compare IgG avidity index with PCR for T. gondii detection results in AF	—	To determine a cut-off value of IgG avidity to predict T. gondii DNA in AF	2015	[19]
AF	BL			To evaluate Se/Sp of PCR on CT diagnosis in AF obtained at birth	—	To compare Se in AF from patients with negative and positive CT diagnosis. To compare postnatal serology and at birth AF regarding early diagnosis ability	—	—	2015	[20]
AF	BL			—	To combine PCR and avidity IgG in order to improve performance diagnosis	To compare conventional ELISA and IgG avidity with PCR (genes B1 and P30) in BL and AF samples for early CT	To associate data of IgG anti-T. gondii titers, avidity index, and PCR to diagnose acute toxoplasmosis	—	2017	[21]
AF	BL			—	—	Comparison of gestational age, parasite load, and positive IgM between symptomatic and asymptomatic groups	—	To correlate T. gondii load, gestational age of maternal infection, and IgM at birth to the signs and severity of CT	2017	[22]
AF	BL			—	—	To compare PCR results for T. gondii in AF to the follow-up screen at birth	—	To describe T. gondii DNA detection in AF. To date maternal T. gondii infection	2018	[23]
	BL			—	—	To compare results obtained in the IgG avidity test with those obtained in the IgM ELISA and AC/HS tests	To evaluate the usefulness of testing for IgG avidity to exclude acute infection	—	2001	[24]
	BL			—	—	Comparison between IgM ELISA and VIDAS IgG avidity. Comparison between VIDAS IgG avidity test and TSp results (IgG, IgA, IgM, and IgE)	To differentiate recently acquired from distant infection using T. gondii IgG avidity (VIDAS kit) and TSp (IgG, IgA, IgM, and IgE)	—	2002	[25]
	BL			—	—	Comparison between individual recombinant antigens, its homogeneous mixture, and whole-cell toxoplasma antigen to determine IgG avidity	To discriminate between acute and latent phases of T. gondii infection by using recombinant antigens for avidity assay	—	2003	[26]
	BL			To evaluate Se/Sp for different AI thresholds	To define a new threshold to improve performance of avidity index for diagnosing chronic infection	—	To correlate time of infection with the avidity index in order to date infection	To evaluate if time and type of treatment influences the avidity index	2004	[27]
	BL			—	—	To compare IgM/IgG ELISA with PCR results performed in blood sample	—	To evaluate PCR utility to detect recent T. gondii infection	2004	[28]
	BL			—	—	—	To evaluate the ability of IgG-avidity to predict the risk of mother-to-child transmission of T. gondii in pregnant women IgG+/IgM+	—	2006	[29]
	BL			To evaluate Se, Sp, PPV, NPV of two commercial kits for acute toxoplasmosis designed to detect IgA and IgG avidity	To combine IgA and IgM tests to improve CT diagnosis	—	—	—	2007	[30]
	BL			—	—	To compare VIDAS avidity test and nested-PCR assay results to confirm ongoing or recent T. gondii infection in the selected group of pregnant women	To detect an ongoing or recent T. gondii infection in pregnant during the first 16 GW by using VIDAS T. gondii specific IgG-avidity test and nested PCR	—	2007	[31]
	BL			—	To improve CT diagnosis by comparison mother and child antibody subclasses (IgG1, IgG2, IgG3, and IgG4)	—	—	—	2008	[32]
	BL			To evaluate Se/Sp of IgG and IgM ELISA tests with rGRA6	—	The comparisons between ELISA GRA6 with ELISA VIDAS and ELISA euroimmun	To investigated rGRA6 potential to differentiate recently acquired infections to those acquired in the distant past	—	2008	[33]
	BL			To evaluate Se/Sp of IgM detection in filter paper-embedded blood	To verify if filter paper-embedded blood can be used for IgM detection. To determine IgG titer and IgG avidity in M-PB embedded in a filter paper	—	—	—	2009	[34]
	BL			To analyze Se/Sp of the ARCHITECT toxo IgG, IgM, and IgG avidity	—	To compare IgG and/or IgM results by ARCHITECT and 2 commercial techniques (AxSYM and VIDAS)	—	—	2009	[35]
	BL			To evaluate the ROC curve analysis of vitros IgM assay values for potential discrimination of acute and chronic infections	—	To compare the vitros IgG and IgM assays to the Sabin–Feldman dye test. To compare vitros Tg IgM to IgM ISAGA	To evaluate a screening serological method to identify chronic and acute Tg infection	—	2009	[36]
	BL			To evaluate Se, Sp, PPV, NPV of MEIA, ELFA, IFAT, and ELISA (IgM e IgA) for CT diagnosis	—	—	—	—	2009	[37]
	BL			To determine Se, Sp, PPV, NPV of combined elecsys IgG and IgM system	—	To compare the new Roche Elecsys T. gondii IgG and IgM immunoassay with Sabin–Feldman dye test and immunosorbent agglutination assay-IgM	To discriminate acute and chronic infection using ROC analysis for Elecsys IgM values	To determine the best cut-off using ROC analysis	2010	[38]
	BL			To evaluate performance of IgG avidity test based on recombinant GRA6 antigen to differentiate recently acquired and distant T. gondii infections	To develop an IgG avidity test based on recombinant GRA6 antigen	To compare ELISA to the euroimmun IgG avidity ELISA for exclusion of a recent Toxoplasma infection that occurred less than 4 months before	To evaluate IgG avidity based on rGRA6 assay ability to differentiate recently acquired and distant T. gondii infections in pregnant women	To determine the best parameters affecting the level of dissociation of antigen-antibody complex	2010	[39]
	BL			—	—	To compare immunoenzymatic, chemiluminescence, and indirect immunofluorescence assay with immunoblot analysis	To assess the immunoassays’ abilities to diagnose seroconversion at its earliest stages	—	2011	[40]
	BL			—	—	—	To evaluate IgG avidity for TC diagnosis in early pregnancy	—	2011	[41]
	BL			—	To improve CT diagnosis by comparing mother and child antibody that target high-molecular-mass T. gondii antigens	—	—	To identify the best immunoblot bands of T. gondii antigens able to differentiate mother and child infection	2012	[42]
	BL			—	To identify potential T. gondii immunogens using pregnant sera and applying immunoproteomics assays	—	—	—	2012	[43]
	BL			To evaluate performance of LFIA for rapid screening of anti-T. gondii antibody in serum and saliva samples from pregnant women	Development of SAG2-LFIA, ROP2-LFIA, and SAG2 + ROP2-LFIA for rapid screening of anti-T. gondii ab in pregnant serum and saliva	To compare LFIA to commercial ELISA	Screening T. gondii IgM, IgG, and IgA avidity by SAG2 + ROP2-LFIA in order to detect recent or acute T. gondii infection	—	2012	[44]
	BL			—	—	The comparisons between PCR targeting the B1 gene and ELISA (IgG and IgM results) assays	—	—	2012	[45]
	BL			—	To determine the impact of additional maternal and/or N-CB serology on improving prenatal screening for CT	Comparison between prenatal and postnatal (M-PB and N-CB) serology	—	—	2013	[46]
	BL			To evaluate performance of IgG/IgM ELISA based on rMEP	To develop IgG/IgM ELISA based on rMEP	To compare rMEP-ELISA to commercial ELISA kits	To differentiate acute from chronic infection using ELISA based on a rMEP	—	2013	[47]
	BL			—	—	To compare EIA-IgG and FAT techniques in order to analyze equivocal or discordant results in routine IgG tests	—	To assess the usefulness of the WB as a confirmatory test to solve discordant results between EIA-IgG and FAT techniques	2013	[48]
	BL			To determine Se, Sp, PPV, NPV of VIDAS, architect and liaison systems for diagnosing T. gondii IgM and IgG	—	To compare anti-T. gondii IgG, IgM, and IgG avidity measurements obtained with three automated systems: VIDAS, architect, and liaison systems	—	To correlate anti-T. gondii IgG avidity measurements between VIDAS and architect and also between VIDAS and liaison systems	2013	[49]
	BL			—	—	To compare homemade WB with the commercial LDBIO II	—	To select the more valuable bands in a homemade WB that can be used as a confirmatory technique for discordant or equivocal results in EIA and FAT	2014	[50]
	BL			To determine Se, Sp, PPV, NPV of avidity assay	—	To compare IgG avidity results with the IgM and IgG ELISA test in a single serum sample	To discriminate acute and chronic infection in a single serum sample using IgG avidity assay	—	2014	[51]
	BL			To evaluate IgM and IgG ELISA Se/Sp based on PCR results	—	To compare immunological methods (ELISA IgM, IgG, and IgG avidity) to PCR based on 529 bp T. gondii DNA fragment	To investigate ELISA IgM and IgG-avidity and PCR results for detection of past or recent toxoplasmosis according to PCR results	—	2014	[52]
	BL			To determine performance of CML, indirect ELISA-rROP2 and IFI for the detection of IgG anti-T. gondii	—	To compare the performance of ELISA-rROP2 to CML and IFI for detection of IgG anti-T. gondii. Comparisons between IgG anti-T. gondii levels obtained from different pregnant groups using ELISA-rROP2 assay	—	—	2015	[53]
	BL			—	—	To compare VIDAS and architect avidity to determine the best method for estimating infection date	To estimate the date of infection	—	2016	[54]
	BL			To evaluate Se, Sp, PPV, NPV, accuracy of IgM IFAT in predicting recent infection according to the GW	—	—	To diagnose acute or chronic T. gondii infection using IgM IFAT	—	2016	[55]
	BL			To analyze AUC, Se, Sp of rP35a and rP22a to discriminate samples from not infected, typical-chronic, presumably acute, and recently chronic infections	Using bioinformatics tools to predict the highest epitopes density regions in P35 and P22 and expressed them for obtaining soluble proteins	To compare rP35a and rP22a performance to discriminate not infected, typical-chronic, presumably acute, and recently chronic infections	To assess the ability of both P35 and P22 antigens to differentiate T. gondii acute and chronic infection stages using indirect and avidity ELISA	—	2017	[56]
	BL			—	—	To compare IgM ELISA and IgG avidity in pregnant women during the first trimester pregnancy	To determine the performance of the IgG avidity test in detecting anti-T. gondii antibodies in pregnant women (IgG+/IgM+)	—	2017	[57]
	BL			—	—	To compare WB (LDBIO II) and automated assays (TGS TA, architect, vidasII, liaisonII, platelia, and Elecsys) concerning ability to detect early T. gondii seroconversion	—	To evaluated time required for anti T. gondii IgG detection by WB and 6 automated assays	2017	[58]
	BL			To determine Se, Sp of IIF, ELISA and IgG avidity tests	—	To compare ELISA, IIF and IgG avidity for diagnosing acute toxoplasmosis using a single serum sample	To discriminate acute and chronic infection using IgG avidity test	To evaluate the frequency of IIF and ELISA positivity using different serum dilutions	2017	[59]
	BL			To determine Se, Sp, PPV, NPV of IA assay based on latex particles	To develop IA assay based on LPC with T. gondii protein (P22Ag) to evaluate its ability of discrimination infected (chronic and acute) and noninfected control	To compare characteristics of LPC coupled with P22Ag and T. gondii homogenate. To compare the performance of LPC made of different compositions	To ruling out acute toxoplasmosis in pregnant women using IA based on LPC	—	2017	[60]
	BL			To evaluate the accuracy, Se, Sp, PPV, NPV of IgA in diagnosis of acute toxoplasmosis in pregnant women	—	To analyze IgA and IgM antibody positivity rates compared to AC/HS and IgG avidity results in pregnant women	To evaluate the usefulness of IgA in diagnosis of acute toxoplasmosis in pregnant women	—	2019	[61]
	BL	PL		To evaluate Se/Sp of methods (PCR, mouse inoculation) in PL and (ISAGA IgM, WB) in N-PB	To combine methods for improving Se diagnosis (PCR + bioassay in PL) or (ISAGA + WB in N-PB) or (PCR + bioassay in PL + ISAGA + WB in N-PB)	—	—	To establish the relationship between maternal treatment and T. gondii detection in PL. To analyze T. gondii strains isolated in PL tissue	2007	[62]
	BL	PL		To evaluate Se, Sp, PPV, NPV of PL for CT diagnosis using PCR and mouse inoculation	To combine mouse inoculation and PCR to improve sensitivity	—	—	To determine if time of maternal treatment or maternal seroconversion is related with PL Se	2010	[63]
AF	BL	PL		To evaluate Se, Sp, PPV, NPV of neonatal diagnosis: T. gondii isolation (PL and CB) and immunological tests (IgA and IgM). To evaluate Se of prenatal diagnosis	To combine prenatal and postnatal diagnosis for improving Se	To compare Se of different diagnosis methods	—	To evaluate treatment effect on diagnosis	2001	[64]
AF	BL	PL		—	—	Comparison between two PCR methods for detecting T. gondii in AF, BL, and tissues	—	—	2004	[65]
AF	BL	PL		To evaluate Se, Sp, PPV, NPV of methods (PCR, mouse inoculation) in AF and PL according to gestational age	—	To compare PCR and mouse inoculation in AF according to gestational age	—	—	2009	[66]
AF	BL	PL		To determine predictive values of molecular diagnosis in AF, PL, and CB	—	—	—	To estimate CT risk based on molecular diagnosis	2012	[67]
AF	BL	PL		To determine Se/Sp of different diagnosis methods and samples (AF, PL CB, and PB)	—	To compare two PCR methods for T. gondii detection in AF, CB, and PB	—	—	2015	[68]
	BL		CL	—	To evaluate CL as an alternative biological sample for CT diagnosis	To compare CL and M-PB samples in the following parameters: IgM, IgG, and IgA levels; IgG avidity against T. gondii antigenic fractions	—	To evaluate the correlation of IgM, IgG, and IgA detection in CL and M-PB samples	2015	[69]

^†AF: amniotic fluid; BL: blood; PL: placenta; CL: colostrum; GW: gestational week. Ab: antibodies; AC/HS: differential agglutination (of acetone (AC)-fixed versus that of formalin (HS)-fixed tachyzoites); AUC: areas under the curve; CML: chemiluminescence; CT: congenital toxoplasmosis; EF: efficiency; EIA: enzyme immune assay; EIA: enzyme immunoassay; ELFA: enzyme-linked fluorescent assay; ELISA-rROP2: enzyme-linked immunoassay using recombinant T. gondii rhoptry 2; FAT: fluorescent antibody test; IA: immunoagglutination; IF: immunofluorescence test; IFAT: indirect‐fluorescent antibody test; IFI: indirect immunofluorescence; ISAGA: immunosorbent agglutination assay; LFIA: lateral flow immunoassay; LPC: latex-protein complexes; MEIA: microparticle enzyme immunoassay; M-PB: maternal peripherical blood; N-CB: neonatal cord blood; NLR: negative likelihood ratio; N-PB: neonatal peripherical blood; NPV: negative predictive value; P-CB: prenatal cord blood; PLR: positive likelihood ratio; PPV: positive predictive value; rGRA6: recombinant dense granule protein 6; rMEP: recombinant multiepitope fusion peptide; rP22a: recombinant soluble protein 22; rP35a: recombinant soluble protein 35; rtPCR: real-time PCR; Se: sensitivity; Sp: specificity; TSp: toxoplasma serological profile; WB: western blot.