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The IOS™ Quantitative hCG Test Cartridges are to be used for the quantitative determination of human chorionic gonadotropin (hCG) in serum for the early detection of pregnancy. They are intended to be used with the IOS™ instrument in clinical laboratories, physicians' office laboratories, and other alternate sites of use close to the point of patient care.

The IOS™ Immunoassay Controls Kit is to be used to assist in monitoring accuracy and precision in the IOS™ immunoassay test cartridges.

Quantitative hCG Test Cartridges: Human chorionic gonadotropin is a glycoprotein that is synthesized by the placenta during pregnancy and appears in both serum and urine relatively soon after implantation of the developing embryo. The presence of hCG, and its rapid rise following conception, is thus the basis of pregnancy testing. (1) Quantitation of hCG can aid in the determination of ectopic pregnancy and spontaneous abortion (2, 3). hCG is also secreted by a wide variety of tumors: gestational trophoblastic tumors, testicular and prostatic tumors, and some breast cancers. (4,5).

Human chorionic gonadotropin is composed of two noncovalently linked polypeptides: the alpha and beta subunits. The individual subunits lack biological activity, but become active when combined to form the intact hormone. The alpha subunit of hCG is structurally homologous to the alpha subunits of LH (luteinizing hormone), FSH (follicle stimulating hormone), and TSH (thyroid stimulating hormone). The beta subunit of each of the hormones is structurally unique and confers the biologic and immunologic specificity to each hormone. The beta subunit of hCG contains a unique chain of 30 carboxy-terminal amino acids that confers its specificity (1). Monoclonal antibodies directed against this portion of the beta subunit permit differentiation between hCG and the other pituitary glycoprotein hormones.

Principle of the Test: The IOS™ Quantitative hCG test is a two-site sandwich immunoassay which utilizes two antibodies directed against hCG: a polyclonal antibody immobilized on the plastic cartridge surface (capture antibody) and a monoclonal antibody labeled with alkaline phosphatase (detection antibody, conjugate). hCG in the patient sample binds to conjugate in the test cartridge, and this hCG-conjugate complex then binds to the immobilized capture antibody. After a short incubation period, unbound hCG-conjugate complex is washed away. Substrate is added, which reacts with the alkaline phosphatase conjugate-hCG-capture antibody 'sandwich' and produces a fluorescent signal. The level of fluorescence is directly proportional to the amount of bound hCG-conjugate, which is directly proportional to the amount of hCG present in the patient sample. All reagents necessary to perform the test are dried in the IOS™ cartridge, and are rehydrated by the addition of patient sample by the operator, or by the addition of buffer by the instrument.

To perform a test, the operator inserts an IOS™ Quantitative hCG cartridge in the IOS™ instrument. When prompted, the operator adds sample well. A second portion of patient sample is diluted off-line, using the dilution vial supplied with the kit, and pipetted into the second well of the test cartridge. The operator starts the test sequence when sample addition is complete. Patient sample rehydrates conjugate dried in the sample well; the conjugate binds to hCG present in the patient serum sample. This hCG-conjugate complex then flows into the incubation/reaction chamber where it binds to the immobilized capture antibody. At the end of the incubation time, unbound sample-conjugate is washed away by buffer. Buffer is used to rehydrate the dried substrate necessary for signal generation and quantitation of hCG, and the rehydrated substrate is then delivered to the incubation/reaction chamber. The fluorescent signal produced is read as a rate by front-surface fluorometry, compared to the rates produced by a series of calibrators stored in the instrument memory, and the amount of hCG present in the patient sample is calculated from the stored calibration curve. If the signal from the first track (undiluted patient serum) is higher than that of the highest calibrator, the instrument will take a reading from the second track (user-diluted sample) to obtain a quantitative value for the patient sample. This increases the assay range 2500 mIU/mL (undiluted track) to 250,000 mIU/mL (diluted track).

Immunoassay Controls: The use of materials derived from human blood to monitor quality control of clinical chemistry testing in the clinical laboratory has been widely established over the past several years. The Biocircuits IOS™ Immunoassay Controls are two levels of bloodbased material for use with Biocircuits IOS™ Test Cartridges.

To run a control, the operator inserts the Control Cartridge (packaged with the controls) into the IOS™ instrument. The instrument reads the lot number and ranges of acceptable values for the control solutions from the Control Cartridge barcode, and then ejects the Control Cartridge. The operator then inserts a test cartridge and follows the instrument prompts to identify the control level, apply control solutions, and begin the test sequence. The IOS™ instrument performs the required buffer additions to rehydrate assay reagents and perform wash steps as necessary, reads the fluorescence signal generated, and calculates and prints the control result just as it would if the cartridge were used to test a patient sample.

Here's a breakdown of the acceptance criteria and study details for the Biocircuits IOS™ Quantitative hCG Test Cartridges and IOS™ Immunoassay Controls, based on the provided text:

Acceptance Criteria and Reported Device Performance

Note: The document states that "it is self-evident from the data and information presented here that the Biocircuits IOS™ Quantitative hCG Test Cartridges are as safe, effective, and perform as well as the Dade Stratus hCG Fluorometric Immunoassay." This implies that the observed performance of the Biocircuits device, as presented in the tables above, is considered acceptable due to its comparability to the legally marketed predicate device (Dade Stratus). Specific numerical acceptance thresholds were not explicitly given in the provided text beyond the comparison itself.

Study Details

1. Sample size used for the test set and the data provenance:

   • Non-Clinical (Manufacturer's Laboratories):
     • Precision:
       • Within-day: n ≥ 19 for each of 3 control levels.
       • Between-day: n ≥ 60 for each of 3 control levels.
     • Accuracy: 165 patient samples (107 neat sera, 58 diluted samples).
     • Data Provenance: Manufacturer's laboratories (implies in-house testing, likely US-based as the company is in Sunnyvale, CA). Retrospective (patient samples were tested, not explicitly clear if newly collected for the study or pre-existing).
   • Clinical (Physicians' Office Laboratories):
     • Precision: n = 39 (Level 1 control), n = 31 (Level 2 control).
     • Accuracy: 121 patient samples.
     • Data Provenance: Three typical physicians' office laboratories (OB/GYN, Internal Medicine, Reproductive Endocrinology/Fertility practice). Samples were "split and sent to the manufacturer's laboratory for retesting on the predicate device," indicating the original testing was done in these clinical sites. Likely US-based. Retrospective (patient samples).
   • Immunoassay Controls (Manufacturer's Laboratories): At least 40 cartridges each for Level 1 and Level 2 controls.
     • Data Provenance: Manufacturer's laboratories.

2. Number of experts used to establish the ground truth for the test set and the qualifications of those experts:

   • The "ground truth" for the accuracy studies was established by comparison to a "commercially available fluorescent enzyme immunoassay" (Dade Stratus) at the manufacturer's laboratory for the non-clinical study, and by the predicate device at the manufacturer's lab for the clinical study.
   • For the clinical study, "medical technologists, medical assistants, and front-office personnel" performed the tests using the IOS™ device. However, the ground truth was essentially the result from the predicate device in the manufacturer's laboratory, not an expert panel.
   • No specific number of experts or their qualifications for establishing ground truth (other than the implied expertise being embedded in the predicate device's performance which was the comparator) is provided.

3. Adjudication method for the test set:

   • Not applicable. The ground truth was established by comparison to a single predicate device (Dade Stratus) or a commercially available fluorescent enzyme immunoassay, not through a consensus or adjudication process of multiple human readers.

4. If a multi reader multi case (MRMC) comparative effectiveness study was done, If so, what was the effect size of how much human readers improve with AI vs without AI assistance:

   • No, an MRMC study was not done. This device is an automated immunoassay system, not an AI-assisted diagnostic tool that would involve human readers interpreting images or data with and without AI. It directly measures hCG levels.

5. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done:

   • Yes, the device operates in a standalone manner. The IOS™ instrument performs the tests, reads the signal, and calculates/prints the result. Human operators interact by inserting cartridges, adding samples, and starting the test sequence, but the analytical process itself is automated. The performance data presented (precision, accuracy) represents the standalone performance of the device.

6. The type of ground truth used:

   • Comparative Reference: The ground truth for accuracy was established by comparing the results of the Biocircuits IOS™ device to those obtained from a "commercially available fluorescent enzyme immunoassay" (Dade Stratus) which is the predicate device. This is a form of comparative ground truth against a well-established and legally marketed method.

7. The sample size for the training set:

   • The document does not explicitly mention a "training set" in the context of a machine learning or AI algorithm. This device is an immunoassay, not a system that uses a trained AI model in the conventional sense. The "training" in this context would implicitly refer to the internal development and calibration of the assay.
   • For the Immunoassay Controls calibration, the ranges were determined by testing in "at least 40 cartridges each, over several days, using several IOS™ instruments." While this isn't a "training set" for an AI, it represents data used to establish the device's operational parameters for controls.

8. How the ground truth for the training set was established:

   • As noted above, there's no explicit "training set" in the AI sense. For the Immunoassay Controls, the "ranges" were established internally by the manufacturer through repeated testing, implying consistency and accuracy with their own established standards and processes. The document suggests that "Your laboratory should establish its own range for these controls over time," indicating a process of ongoing internal validation.

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