ORTHO T. CRUZI ELISA TEST SYSTEM

K072732 · Ortho-Clinical Diagnostics, Inc. · MIU · Apr 15, 2009 · Microbiology

Device Facts

• Record ID: K072732
• Device Name: ORTHO T. CRUZI ELISA TEST SYSTEM
• Applicant: Ortho-Clinical Diagnostics, Inc.
• Product Code: MIU · Microbiology
• Decision Date: Apr 15, 2009
• Decision: SESE
• Submission Type: Traditional
• Regulation: 21 CFR 866.3870
• Device Class: Class 1

Indications for Use

ORTHO T. cruzi ELISA Test System is an enzyme-linked immunosorbent assay for the in vitro qualitative detection of antibodies (Immunoglobulin G) to Trypanosoma cruzi (T. cruzi) in human adult serum (glass, plastic, or serum separator tubes) and plasma (EDTA, lithium heparin or citrate) using whole-cell lysate antigens. Reactive assay results are presumptive evidence of past infection, and in conjunction with other serological and clinical information, may be used for the laboratory diagnosis of individuals with Chagas' disease. Definitive diagnosis of an acute phase of infection (including acute congenital infection) must be made by alternate methods, e.g., hemoculture, blood smear. This test is not intended for use on samples of cord blood or screening blood or plasma donors.

Device Story

The ORTHO T. cruzi ELISA Test System is an enzyme-linked immunosorbent assay (ELISA) used in CLIA-certified clinical laboratories to detect human IgG antibodies to T. cruzi. The device uses microwells coated with whole-cell lysate antigens from T. cruzi. Patient serum or plasma is incubated in the wells; if T. cruzi antibodies are present, antigen-antibody complexes form. A murine monoclonal anti-human IgG conjugated with horseradish peroxidase is added, followed by a chromogenic substrate (o-phenylenediamine and hydrogen peroxide). The reaction is stopped with sulfuric acid, and the resulting color intensity is measured spectrophotometrically. The optical density correlates with the concentration of T. cruzi antibodies. Results are interpreted by healthcare providers to aid in the diagnosis of Chagas' disease. The device provides presumptive evidence of past infection but is not for acute phase diagnosis or blood donor screening.

Clinical Evidence

Clinical performance evaluated in a multi-center study (N=1074 high/low risk subjects; N=106 parasite-positive; N=810 serologically presumed positive). Compared against T. cruzi IFA and supplemental RIPA. In high/low risk populations, positive percent agreement with most probable status was 98.92% (94.15-99.97% CI) and negative percent agreement was 99.39% (98.67-99.78% CI). In parasite-positive subjects, sensitivity was 100% (96.58-100% CI). Analytical specificity testing (N=616) showed potential cross-reactivity with Leishmania (79% reactive).

Technological Characteristics

ELISA-based serological assay. Uses whole-cell lysate antigens coated on plastic microwells. Detection via horseradish peroxidase-conjugated anti-human IgG and o-phenylenediamine (OPD) substrate. Requires spectrophotometric reader (490/492 nm with 620/630 nm reference). Compatible with semi-automated instrumentation (pipettors, washers, incubators).

Indications for Use

Indicated for in vitro qualitative detection of IgG antibodies to T. cruzi in human adult serum or plasma. Used as an aid in the diagnosis of Chagas' disease in conjunction with other clinical/serological information. Not for use on cord blood or blood/plasma donor screening. Definitive diagnosis of acute infection requires alternate methods.

Regulatory Classification

Identification

Trypanosoma spp. serological reagents are devices that consist of antigens and antisera used in serological tests to identify antibodies to Trypanosoma spp. in serum. The identification aids in the diagnosis of trypanosomiasis, a disease caused by parasitic protozoans belonging to the genus Trypanosoma. Trypanosomiasis in adults is a chronic disease characterized by fever, chills, headache, and vomiting. Central nervous system involvement produces typical sleeping sickness syndrome: physical exhaustion, inability to eat, tissue wasting, and eventual death. Chagas disease, an acute form of trypanosomiasis in children, most seriously affects the central nervous system and heart muscle.

Predicate Devices

• Hemagen Chagas' Kit (EIA Method) (K930272)
• Enzyme Linked Immunosorbent Assay, T. cruzi - Wiener Laboratories (K023889)

Submission Summary (Full Text)

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# 510(k) SUBSTANTIAL EQUIVALENCE DETERMINATION DECISION SUMMARY ASSAY ONLY TEMPLATE

A. 510(k) Number:
K072732

B. Purpose for Submission:
To obtain device clearance

C. Measurand:
Trypanosoma cruzi (T. cruzi)

D. Type of Test:
ELISA

E. Applicant:
Ortho Clinical Diagnostics

F. Proprietary and Established Names:
ORTHO® T. Cruzi ELISA Test System

G. Regulatory Information:
1. Regulation section:
866.3870
2. Classification:
1
3. Product code:
MIU
4. Panel:
Microbiology

H. Intended Use:
1. Intended use(s):
ORTHO T. cruzi ELISA Test System is an enzyme-linked immunosorbent assay for the in vitro qualitative detection of antibodies (Immunoglobulin G) to Trypanosoma cruzi (T. cruzi) in human adult serum (glass, plastic, or serum separator tubes) and plasma (EDTA, lithium heparin or citrate) using whole-cell lysate antigens. Reactive assay results are presumptive evidence of past infection, and in conjunction with other serological and clinical information, may be used for the laboratory diagnosis of individuals with Chagas' disease.
Definitive diagnosis of an acute phase of infection (including acute congenital infection) must be made by alternate methods, e.g., hemoculture, blood smear.

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This test is not intended for use on samples of cord blood or screening blood or plasma donors.

2. **Indication(s) for use:**

ORTHO *T. cruzi* ELISA Test System is an enzyme-linked immunosorbent assay for the *in vitro* qualitative detection of antibodies (Immunoglobulin G) to *Trypanosoma cruzi* (*T. cruzi*) in human adult serum (glass, plastic, or serum separator tubes) and plasma (EDTA, lithium heparin or citrate) using whole-cell lysate antigens. Reactive assay results are presumptive evidence of past infection, and in conjunction with other serological and clinical information, may be used for the laboratory diagnosis of individuals with Chagas’ disease.

Definitive diagnosis of an acute phase of infection (including acute congenital infection) must be made by alternate methods, e.g., hemoculture, blood smear.

This test is not intended for use on samples of cord blood or screening blood or plasma donors.

3. **Special conditions for use statement(s):**

NA

4. **Special instrument requirements:**

NA

I. **Device Description:**

The assay procedure is a three-stage test carried out in a microwell coated with lysate (antigens) prepared from *T. cruzi*. In the first stage, test specimen, Negative Control, and Positive Calibrator are diluted directly in the test well containing Specimen Diluent, and incubated for a specified length of time. If antibodies to *T. cruzi* are present, antigen-antibody complexes will form on the microwell surface. If antibodies to *T. cruzi* are absent, complexes will not form. Unbound antibodies in the sample will be removed during the subsequent wash step.

In the second stage, murine monoclonal antibody conjugated with Horseradish Peroxidase (Conjugate) is added to the test well. The Conjugate binds specifically to the antibody portion of the antigen-antibody complex. If complexes are not present, the unbound Conjugate is removed by the subsequent wash step.

In the third stage, an enzyme detection system composed of *o*-phenylenediamine (OPD) and hydrogen peroxide is added to the test well. If bound Conjugate is present, the OPD will be oxidized, resulting in a colored end product. Sulfuric acid is then added to stop the reaction. The color intensity depends on the amount of bound Conjugate and, therefore, is a function of the concentration of antibodies to *T. cruzi* present in the specimen. The intensity of color in the substrate solution is then determined with a microwell reader (spectrophotometer) designed to measure light absorbance in a microwell.

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J. Substantial Equivalence Information:

1. Predicate device names:
Hemagen Chagas Kit (EIA Method)
Wiener Laboratories T. cruzi – Enzyme Linked Immunosorbent Assay,

2. Predicate 510(k) numbers:
K930272
K023889

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# 3. Comparison with predicate:

| | New Device | Predicate Device | Predicate Device |
| --- | --- | --- | --- |
| Device Characteristic | ORTHO T. cruzi ELISA Test System | K930272 Hemagen Chagas' Kit (EIA Method) – Hemagen Diagnostics, Inc. | K023889 Enzyme Linked Immunosorbent Assay, T. cruzi – Wiener Laboratories |
| Intended Use | ... for the in vitro qualitative detection of antibodies to Trypanosoma cruzi (T. cruzi) | ... for the detection of circulating antibodies to Trypanosoma cruzi, the causative agent of Chagas' disease | Qualitative detection of antibody to Trypanosoma cruzi, the causative agent for Chagas' disease in human serum or plasma. |
| Indications for Use | Assay results, in conjunction with other serological and clinical information, may be used for the laboratory diagnosis of individuals with Chagas' disease. | When used according to instructions, the kit is useful in exhibiting prior exposure to T. cruzi and as an aid in the diagnosis of Chagas' disease. | When using according to instructions, the kit is useful in establishing prior exposure to T. cruzi and as an aid in the diagnosis of Chagas' disease. |
| Basic Principle | Enzyme-linked immunosorbent assay, ELISA | Enzyme-linked immunosorbent assay, ELISA | Enzyme-linked immunosorbent assay, ELISA |
| Where used | CLIA Certified Clinical Laboratory | CLIA Certified Clinical Laboratory | CLIA Certified Clinical Laboratory |
| Sample Type | Serum or Plasma (EDTA, lithium heparin or citrate) | Serum | Serum or Plasma (heparin, EDTA, and citrate based anticoagulants) |
| Antigen | Trypanosoma spp. (T. cruzi Tulahuen) | Trypanosoma spp. | Recombinant T. cruzi antigens from the trypomastigote parasite stage, #1, #2, #13, #30, and #36) |
| Antigen Prep | Whole cell lysate coated onto plastic microwells | Purified antigens from cultured T. cruzi organisms | Recombinant technology |
| Sample Volume | 20 μL | 10 μL | 10 μL |
| Procedure | Diluted sample is incubated with the antigen prep. After an appropriate time the serum dilution in removed, and the antigen prep is washed. The antigen prep is overlaid with antibody labeled with an chromogenic substrate | Diluted sample is incubated with the antigen prep. After an appropriate time the serum dilution in removed, and the antigen prep is washed. The antigen prep is overlaid with antibody labeled with an chromogenic substrate | Diluted sample is incubated with the antigen prep. After an appropriate time the serum dilution in removed, and the antigen prep is washed. The antigen prep is overlaid with antibody labeled with an chromogenic substrate |
| Conjugate Antibody | Anti-human IgG | Anti-human IgG | Anti-human IgG |
| Tracer | Horseradish peroxidase with a Substrate Solution made from Substrate Buffer and OPD Tablets | Horseradish peroxidase with substrate 3, 3', 5, 5' – tetramethylbenzidine (TMB) | Horseradish peroxidase with substrate 3, 3', 5, 5' – tetramethylbenzidine (TMB) |
| Antibodies Detection | The antibody-HRP bound to the whole cell lysate-antibody complex reacts with the OPD producing a colored end product. The OD is read spectrophotometrically | The antibody-HRP bound to the whole cell lysate-antibody complex reacts with the TMB producing a colored end product. The OD is read spectrophotometrically | The antibody-HRP bound to the recombinant antigens-antibody complex reacts with the TMB producing a colored end product. The OD is read spectrophotometrically |

N.B.: Shaded areas show differences between the device and the predicates

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K. Standard/Guidance Document Referenced (if applicable):
NA

L. Test Principle:
See device description

M. Performance Characteristics (if/when applicable):

1. Analytical performance: NA

a. Precision/Reproducibility:
The intra-assay (within plate) and inter-assay (between plates) precision of the ORTHO T. cruzi ELISA Test System was evaluated using an eight-member precision panel. The precision panel consisted of three moderate to strongly reactive samples, three reactive samples near the assay cutoff (approximately 1.5 – 2.0 S/C), and two nonreactive samples. The panel was tested at three external sites using three different kit lots by the semi-automated processing method. Ten replicates each of the eight-member panel were assayed on a single occasion per day on nine different days by two technologists for a total of 4319 observations (one observation for R7 was a statistical outlier). Mean signal to cutoff (S/C), standard deviation (SD), and coefficient of variation (CV %) results are presented in the table below.

| Panel Member | Number Tested | Mean ORTHO T. cruzi ELISA S/C | Inter-assay^{1} | | Intra-assay^{2} | | Total^{3} | |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| | | | SD | CV(%) | SD | CV(%) | SD | CV(%) |
| R1 | 540 | 5.954 | 0.258 | 4.3 | 0.324 | 5.4 | 0.492 | 8.3 |
| R2 | 540 | 6.424 | 0.306 | 4.8 | 0.324 | 5.0 | 0.501 | 7.8 |
| R3 | 540 | 6.647 | 0.338 | 5.1 | 0.345 | 5.2 | 0.554 | 8.3 |
| R4 | 540 | 1.946 | 0.089 | 4.6 | 0.143 | 7.3 | 0.189 | 9.7 |
| R5 | 540 | 1.909 | 0.097 | 5.1 | 0.128 | 6.7 | 0.180 | 9.4 |
| R6 | 540 | 2.173 | 0.113 | 5.2 | 0.134 | 6.2 | 0.207 | 9.5 |
| R7 | 539 | 0.084 | 0.011 | N/A^{4} | 0.025 | N/A^{4} | 0.031 | N/A^{4} |
| R8 | 540 | 0.101 | 0.013 | N/A^{4} | 0.029 | N/A^{4} | 0.035 | N/A^{4} |
| 1 Between Plate (Between Run (Lot x Site x Technologist)): Variability of the assay performance from plate to plate
2 Within Plate (Between Replicate): Variability of the assay performance from replicate to replicate
3 Total: Inter-assay and Intra-assay variability
4 % CVs are not meaningful when S/C approaches zero | | | | | | | | |

b. Linearity/assay reportable range:
NA

c. Traceability, Stability, Expected values (controls, calibrators, or methods):
NA

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d. Detection limit:

NA

e. Analytical specificity:

The specificity of the ORTHO T. cruzi ELISA Test System was evaluated using 616 samples from individuals with infections or clinical conditions that might potentially exhibit cross reactivity when tested with the assay. The table below shows the numbers and types of samples tested.

| Potentially Cross Reacting Condition or Disease State | Number of Specimens | Nonreactive (%) | Repeatedly Reactive (%) |
| --- | --- | --- | --- |
| Leishmania1 | 100 | 21 (21.0) | 79 (79.0) |
| Malaria | 96 | 94 (97.9) | 2 (2.1) |
| Schistosomiasis | 30 | 30 (100.0) | 0 (0) |
| Syphilis | 30 | 29 (96.7) | 1 (3.3) |
| Pre-Vaccination with Influenza Vaccine | 35 | 35 (100.0) | 0 (0) |
| Post-Vaccination with Influenza Vaccine | 35 | 35 (100.0) | 0 (0) |
| Lupus Erythematosus (ANA titer > 1:640) | 30 | 30 (100.0) | 0 (0) |
| Rheumatoid Arthritis (RF > 30 IU or titer > 1:320) | 30 | 30 (100.0) | 0 (0) |
| Polyclonal Gammopathies | 15 | 15 (100.0) | 0 (0) |
| Monoclonal Gammopathies | 15 | 15 (100.0) | 0 (0) |
| Multiple Leukocyte Alloantibodies | 15 | 15 (100.0) | 0 (0) |
| Multiple Red Cell Alloantibodies | 15 | 15 (100.0) | 0 (0) |
| Cytomegalovirus | 20 | 20 (100.0) | 0 (0) |
| Epstein-Barr Virus | 20 | 20 (100.0) | 0 (0) |
| Herpes Simplex Virus Type 1 | 20 | 20 (100.0) | 0 (0) |
| Rubella | 20 | 20 (100.0) | 0 (0) |
| Hepatitis B | 20 | 20 (100.0) | 0 (0) |
| Hepatitis C | 20 | 20 (100.0) | 0 (0) |
| Human Immunodeficiency Virus | 20 | 20 (100.0) | 0 (0) |
| Human T-Cell Lymphotropic Virus | 20 | 20 (100.0) | 0 (0) |
| Toxoplasmosis gondii | 5 | 5 (100.0) | 0 (0) |
| Paracoccidioides brasiliensis | 5 | 3 (60.0) | 2 (40.0)2 |
| Total | 616 | 532 (86.4) | 84 (13.6) |
| 1Leishmania specimens were collected in India where T. cruzi is not endemic and these specimens are presumed to be T. cruzi antibody negative2These two specimens were obtained from Argentina, where T. cruzi infection is endemic. Both specimens were RIPA positive. | | | |

Among the 100 subjects with Leishmania infection, 21 (21.0%) were nonreactive and 79 (79.0%) were repeatedly reactive. The specimens were obtained in India where T. cruzi is not endemic and, therefore, the most probable T. cruzi antibody status of the 100 Leishmania specimens is negative. The ORTHO T. cruzi ELISA Test System may yield falsely reactive results among test subjects with no Leishmania infection.

Of the 516 non-Leishmania specimens, 511 (99.0%) were nonreactive and five (1.0%) were repeatedly reactive. Three of the five repeatedly reactive specimens (1 syphilis, and 2 malaria, $P$ . falciparum) were RIPA negative. Two of the five repeatedly reactive specimens were obtained

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from among the five test subjects with Paracoccidioides brasiliensis infection. These two specimens were RIPA positive and were obtained from a T. cruzi endemic area. Whether these represent false positive for T. cruzi infection due to cross reactivity in both ELISA and RIPA or co-infection with P. brasiliensis and T. cruzi is not known.

f. Assay cut-off:

NA

2. Comparison studies:

a. Method comparison with predicate device:

See 3c.

b. Matrix comparison:

NA

3. Clinical studies:

a. Clinical Sensitivity:

See 3. c.

b. Clinical specificity:

See 3. c.

c. Other clinical supportive data (when a. and b. are not applicable):

Clinical Performance

A multi-center study was conducted to establish the clinical performance of the ORTHO T. cruzi ELISA Test System among individuals at high or low risk for T. cruzi infection selected under well-defined inclusion and exclusion criteria but without regard to a known or previously determined T. cruzi antibody assay result. Statistical testing was performed to ensure that the distribution of ORTHO T. cruzi ELISA S/C values was homogeneous across the two testing sites participating in the study (Camp Hill, PA and Newark, NJ), and that the test results could be combined for analysis. Individuals presumed to be T. cruzi antibody positive by parasite detection methods or by serological methods were evaluated separately.

Specimens from subjects at high risk for T. cruzi infection (N=574) were collected in Bolivia (28.9%), Colombia (13.1%), Guatemala (23.3%), Mexico (8.7%) and Nicaragua (26.0%). The population was 44.9% female and 55.1% male, and ranged in age from 18 to 88 years.

Specimens from subjects at low risk for T. cruzi infection but with signs or symptoms similar to Chagas' disease (N=300) were collected in the U.S. from Black (7.7%) and Caucasian (92.3%) subjects. The population was 43.0% female and 57.0% male, and ranged in age from 21 to 93 years. Specimens from low risk pregnant women (N=200) were obtained in the U.S. from subjects in their first (21.5%), second (38.5%) or third (40.0%) trimester.

Comparator testing was performed with a validated T. cruzi IFA. Additional, more specific supplemental testing was performed with a validated T. cruzi radioimmunoprecipitation assay (RIPA).

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# ORTHO T. cruzi ELISA and T. cruzi IFA Results among High Risk and Low Risk Subjects

Specimens from 1074 subjects at high or low risk for *T. cruzi* infection were tested with a comparator *T. cruzi* IFA and with the ORTHO *T. cruzi* ELISA Test System. The results are presented in the following table.

| ORTHO T. cruzi ELISA vs. T. cruzi IFA Results (N=1074) | | | |
| --- | --- | --- | --- |
| ORTHO T. cruzi ELISA Result | T. cruzi IFA Result | | Total |
| | Positive | Negative | |
| Repeatedly Reactive | 82 | 16^{2} | 98 |
| Nonreactive | 3^{1} | 973 | 976 |
| Total | 85 | 989 | 1074 |
| ^{1} These three specimens were also negative with the T. cruzi RIPA.
^{2} Ten of these 16 specimens were also positive with the T. cruzi RIPA. | | | |

# Percent Agreement

The table below summarizes the percent agreement between the ORTHO *T. cruzi* ELISA and the *T. cruzi* IFA. Data are listed by population and overall, with positive and negative percent agreement and 95% exact confidence intervals (CI).

| Positive and Negative Percent Agreement of the ORTHO T. cruzi ELISA with the T. cruzi IFA by Study Population (N=1074) | | | | |
| --- | --- | --- | --- | --- |
| Population | Positive Percent Agreement | 95% Exact Confidence Interval | Negative Percent Agreement | 95% Exact Confidence Interval |
| High Risk | 96.47%
(82/85) | 90.03% - 99.27% | 96.93%
(474/489) | 94.99% - 98.27% |
| Low Risk | | | 100%
(300/300) | 98.78% - 100% |
| Pregnancy
Low Risk | | | 99.50%
(199/200) | 97.25% - 99.99% |
| Total | 96.47%
(82/85) | 90.03% - 99.27% | 98.38% (973/989) | 97.39% - 99.07% |

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# ORTHO T. cruzi ELISA Results and Most Probable T. cruzi Antibody Status among High Risk and Low Risk Subjects

Because the T. cruzi IFA is a non-reference standard for detection of antibodies to T. cruzi, the most probable T. cruzi antibody status of the high and low risk study subjects was determined by ORTHO T. cruzi ELISA Test System, comparator T. cruzi IFA and supplemental T. cruzi RIPA testing according to a pre-specified testing algorithm. Specimens not tested with RIPA that were negative with both the ORTHO T. cruzi ELISA and the T. cruzi IFA were assigned a most probable T. cruzi antibody status of negative. Specimens tested with the RIPA were assigned a most probable T. cruzi antibody status of positive, negative or indeterminate based on the RIPA results.

A comparison of the ORTHO T. cruzi ELISA results to most probable T. cruzi antibody status is presented in the following table.

| ORTHO T. cruzi ELISA Results and Most Probable T. cruzi Antibody Status in the High Risk and Low Risk Populations (N=1074) | | | | |
| --- | --- | --- | --- | --- |
| ORTHO T. cruzi ELISA Results | Most Probable T. cruzi Antibody Status | | | |
| | Positive | Negative | Indeterminate¹ | TOTAL |
| Repeatedly Reactive | 92 | 6 | 0 | 98 |
| Nonreactive | 1 | 975 | 0 | 976 |
| TOTAL | 93 | 981 | 0 | 1074 |
| ¹ There were no T. cruzi RIPA indeterminate results and therefore no specimens with a most probable T. cruzi antibody status of indeterminate among the high and low risk specimens. | | | | |

# Percent Agreement

The table below summarizes the percent agreement between the ORTHO T. cruzi ELISA and most probable T. cruzi antibody status. Data are listed by population and overall, with positive and negative percent agreement and 95% exact confidence intervals.

| Positive and Negative Percent Agreement of the ORTHO T. cruzi ELISA with Most Probable T. cruzi Antibody Status by High Risk and Low Risk Study Population (N=1074) | | | | |
| --- | --- | --- | --- | --- |
| Population | Positive Percent Agreement | 95% Exact Confidence Interval | Negative Percent Agreement | 95% Exact Confidence Interval |
| High Risk | 98.92% (92/93) | 94.15% - 99.97% | 98.96% (476/481) | 97.59% - 99.66% |
| Low Risk | | | 100% (300/300) | 98.78% - 100% |
| Pregnancy Low Risk | | | 99.50% (199/200) | 97.25% - 99.99% |
| Total | 98.92% (92/93) | 94.15% - 99.97% | 99.39% (975/981) | 98.67% - 99.78% |

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# Performance with Presumed T. cruzi Antibody Positive Populations

## Specimens Positive for T. cruzi by Parasite Detection Methods

The sensitivity of the ORTHO T. cruzi ELISA Test System was evaluated among subjects classified as parasite positive by historical identification of T. cruzi parasites (N=106). The samples were obtained from the endemic countries of Bolivia (27.3%), Chile (40.6%), Colombia (28.3%), and Nicaragua (3.8%), and were tested with the ORTHO T. cruzi ELISA at one testing site in St. Paul, MN. Specimens in this group were considered to have a most probable T. cruzi antibody status of positive. Assay sensitivity and 95% exact confidence interval are shown in the following table.

| Sensitivity and 95% Exact Confidence Interval for the ORTHO T. cruzi ELISA in Parasite Detection Positive Specimens (N=106) | | |
| --- | --- | --- |
| Population | Sensitivity (%) | 95% Exact Confidence Interval |
| Parasite Detection Positive | 100% (106 / 106) | 96.58% – 100% |

## Specimens Presumed Positive for Antibodies to T. cruzi by Serological Methods

### ORTHO T. cruzi ELISA versus T. cruzi IFA

A total of 810 specimens were included in the T. cruzi serological presumed positive population based upon two positive serological tests for T. cruzi antibodies in use in the countries of origin (i.e., ELISA, IFA, hemagglutination, or complement fixation). The comparator T. cruzi IFA was not used to admit specimens to the study. The specimens were obtained from the endemic countries of Bolivia (17.8%), Brazil (24.7%), Chile (10.6%), Guatemala (2.2%), Mexico (32.5%) and Nicaragua (12.2%). ORTHO T. cruzi ELISA testing was performed at two testing sites in Camp Hill, PA and Newark, NJ. Direct comparison of the ORTHO T. cruzi ELISA with the T. cruzi IFA is presented in the following table.

| ORTHO T. cruzi ELISA vs. T. cruzi IFA Results in Specimens Presumed Positive by Serologic Methods (N=810) | | | |
| --- | --- | --- | --- |
| ORTHO T. cruzi ELISA Result | T. cruzi IFA Result | | Total |
| | Positive | Negative | |
| Repeatedly Reactive | 565 | 99^{2} | 664 |
| Nonreactive | 5^{1} | 141^{3} | 146 |
| Total | 570 | 240 | 810 |
| 1 These five specimens were also negative with the T. cruzi RIPA.
2 Ninety-seven of these 99 specimens were also positive with the T. cruzi RIPA.
3 All 141 specimens were negative with the T. cruzi RIPA. | | | |

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# Percent Agreement

Positive, negative and overall percent agreement of the ORTHO T. cruzi ELISA with the T. cruzi IFA and 95% exact confidence intervals are shown in the following table.

| Positive, Negative and Overall Percent Agreement of the ORTHO T. cruzi ELISA with the T. cruzi IFA in the Serological Presumed Positive Population (N=810) | | | | | | |
| --- | --- | --- | --- | --- | --- | --- |
| Population | Positive Percent Agreement | 95% Exact Confidence Interval | Negative Percent Agreement | 95% Exact Confidence Interval | Overall Percent Agreement | 95% Exact Confidence Interval |
| Serological Presumed Positive | 99.13% (565/570) | 97.96% - 99.71% | 58.75% (141/240) | 52.24% - 65.04% | 87.16% (706/810) | 84.66% - 89.39% |

# ORTHO T. cruzi ELISA versus Most Probable T. cruzi Antibody Status

Because the T. cruzi IFA is a non-reference standard for detection of antibodies to T. cruzi, the most probable T. cruzi antibody status of the study subjects presumed positive by serologic methods was determined by ORTHO T. cruzi ELISA Test System, comparator T. cruzi IFA and supplemental T. cruzi RIPA testing according to a pre-specified testing and interpretation algorithm. Specimens that were ORTHO T. cruzi ELISA repeatedly reactive and positive with the T. cruzi IFA were assigned a most probable T. cruzi antibody status of positive and were not tested with the T. cruzi RIPA. All specimens negative with both assays or with discordant results between the two assays were tested with the T. cruzi RIPA and assigned a most probable T. cruzi antibody status based upon the RIPA results. A comparison of ORTHO T. cruzi ELISA results and most probable T. cruzi antibody status is presented in the following table

| ORTHO T. cruzi ELISA Results and Most Probable T. cruzi Antibody Status in the Serological Presumed Positive Population (N=810) | | | | |
| --- | --- | --- | --- | --- |
| ORTHO T. cruzi ELISA Results | Most Probable T. cruzi Antibody Status | | | TOTAL |
| | Positive | Negative | Indeterminate¹ | |
| Repeatedly Reactive | 662 | 2 | 0 | 664 |
| Nonreactive | 0 | 146 | 0 | 146 |
| TOTAL | 662 | 148 | 0 | 810 |
| ¹ There were no T. cruzi RIPA indeterminate results and therefore no specimens with a most probable T. cruzi antibody status of indeterminate among the serological presumed positive specimens tested with RIPA. | | | | |

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# Percent Agreement

Positive, negative and overall percent agreement of the ORTHO T. cruzi ELISA with most probable T. cruzi antibody status and 95% exact confidence intervals are shown in the following table.

| Positive, Negative and Overall Percent Agreement of the ORTHO T. cruzi ELISA with Most Probable T. cruzi Antibody Status for the Serological Presumed Positive Population (N=810) | | | | | | |
| --- | --- | --- | --- | --- | --- | --- |
| Population | Positive Percent Agreement | 95% Exact Confidence Interval | Negative Percent Agreement | 95% Exact Confidence Interval | Overall Percent Agreement | 95% Exact Confidence Interval |
| Serological Presumed Positive | 100% (662/662) | 99.44% - 100% | 98.65% (146/148) | 95.20% - 99.84% | 99.75% (808/810) | 99.11% - 99.97% |

4. Clinical cut-off:
NA

5. Expected values/Reference range:
NA

N. Proposed Labeling:
The labeling is sufficient and it satisfies the requirements of 21 CFR Part 809.10.

O. Conclusion:
The submitted information in this premarket notification is complete and supports a substantial equivalent decision.