TABLE 1
TABLE 1General Interpretation of Toxoplasma gondii Serologic Results Obtained with Commercial Assays
IgG resultIgM resultInterpretation and follow-up testing in humans, except infants
NegativeNegativeNo serologic evidence of T. gondii infection
NegativeEquivocalPossible early acute T. gondii infection or a false-positive IgM reaction: in 2 to 3 weeks, obtain a new specimen for IgG and IgM testing; if the results for the second specimen remain the same, the patient probably is not infected.
NegativePositivePossible acute T. gondii infection or a false-positive IgM reaction: in 2 to 3 weeks, obtain a new specimen for IgG and IgM testing; if the results for the second specimen remain the same, the IgM reaction is probably a false positive.
EquivocalNegativeIndeterminate: Obtain a new specimen for testing or retest this specimen for IgG using a different assay.
EquivocalEquivocalIndeterminate: Obtain a new specimen for IgG and IgM testing.
EquivocalPositivePossible acute T. gondii infection: in 2 to 3 weeks, obtain a new specimen for IgG and IgM testing; if the results for the second specimen remain the same or the IgG test becomes positive, both specimens should undergo further testing in a reference laboratory with experience in the diagnosis of toxoplasmosis.
PositiveNegativeInfected with T. gondii usually for more than 6 months.
PositiveEquivocalInfected with T. gondii but equivocal IgM results may be due to recent infection or a false-positive IgM reaction: in 2 to 3 weeks, obtain a new specimen for IgM testing; if the results for the second specimen remain the same, both specimens should undergo further testing in a reference laboratory with experience in the diagnosis of toxoplasmosis.
PositivePositivePossible T. gondii infection within the past 12 months or a false-positive IgM reaction: the specimen should undergo further testing in a reference laboratory with experience in the diagnosis of toxoplasmosis.
Adapted with permission from Wilson M, McAuley JM. Toxoplasma. In: Murray PR, ed. Manual of clinical microbiology. 7th ed. Washington, D.C.: American Society for Microbiology, 1999:1379.IgG resultIgM resultInterpretation and follow-up testing in humans, except infants
NegativeNegativeNo serologic evidence of T. gondii infection
NegativeEquivocalPossible early acute T. gondii infection or a false-positive IgM reaction: in 2 to 3 weeks, obtain a new specimen for IgG and IgM testing; if the results for the second specimen remain the same, the patient probably is not infected.
NegativePositivePossible acute T. gondii infection or a false-positive IgM reaction: in 2 to 3 weeks, obtain a new specimen for IgG and IgM testing; if the results for the second specimen remain the same, the IgM reaction is probably a false positive.
EquivocalPositivePossible acute T. gondii infection: in 2 to 3 weeks, obtain a new specimen for IgG and IgM testing; if the results for the second specimen remain the same or the IgG test becomes positive, both specimens should undergo further testing in a reference laboratory with experience in the diagnosis of toxoplasmosis.
PositiveNegativeInfected with T. gondii usually for more than 6 months.
PositiveEquivocalInfected with T. gondii but equivocal IgM results may be due to recent infection or a false-positive IgM reaction: in 2 to 3 weeks, obtain a new specimen for IgM testing; if the results for the second specimen remain the same, both specimens should undergo further testing in a reference laboratory with experience in the diagnosis of toxoplasmosis.
PositivePositivePossible T. gondii infection within the past 12 months or a false-positive IgM reaction: the specimen should undergo further testing in a reference laboratory with experience in the diagnosis of toxoplasmosis.
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