SOP-CM-004 — Urine Qualitative Beta-hCG Pregnancy Test SOP

1.0 Purpose

This SOP sets out the procedure for the qualitative detection of human chorionic gonadotropin (hCG) in urine at Tarangnan Community Hospital using the Abbott Bioline hCG rapid immunochromatographic cassette. It is used for the early detection of pregnancy in routine and emergency clinical consultations.

2.0 Scope

This procedure applies to all qualitative urine pregnancy examinations performed in the Clinical Microscopy Section and at point-of-care emergency testing stations of Tarangnan Community Hospital. It covers specimen collection, room-temperature equilibration, device inoculation, procedural timing, result interpretation, and clinical limitation management.

3.0 Definitions

• Human Chorionic Gonadotropin (hCG): A glycoprotein hormone produced by the syncytiotrophoblast of the developing placenta shortly after fertilization, consisting of an alpha (α) subunit identical to LH, FSH, and TSH, and a unique beta (β) subunit conferring immunological specificity.
• Analytical Sensitivity (Cutoff): The lowest analyte concentration reliably detected by the assay; for the Abbott Bioline hCG kit, this is exactly 25 mIU/mL in urine.
• Lateral-Flow Immunochromatography: An analytical method where liquid specimen migrates along a membrane by capillary action, binding to colloidal gold-labeled antibodies and capturing on immobilized test and control lines.
• Procedural Control Band (C): An internal control line composed of immobilized anti-mouse antibodies that captures gold-conjugated reagent, confirming adequate fluid migration and chromatographic functionality.
• High-Dose Hook Effect (Prozone Phenomenon): A false-negative or paradoxically weakened test line occurring when extraordinarily high antigen concentrations simultaneously saturate both capture and detector antibodies without forming the detection sandwich.

4.0 Responsibility

4.1 Hospital Director

• Grants final approval for this analytical SOP.
• Ensures Abbott Bioline hCG test kits are procured and kept in stock.

4.2 Pathologist

• Provides clinical consultation on equivocal pregnancy test results, suspected trophoblastic disease, or ectopic pregnancy.
• Advises attending medical officers on confirmatory quantitative serum hCG testing when urinary results are discordant with clinical findings.

4.3 Chief Medical Technologist / Laboratory Quality Manager

• Maintains and updates this SOP, ensuring staff training and annual competency verification.
• Enforces proper kit storage conditions (1 to 30 °C), monitors lot-to-lot verification, and reviews daily QC logs.
• Investigates invalid cassette rates and reagent nonconformances per LAB-QM-010.

4.4 Medical Technologists

• Inspect urine specimens for volume, turbidity, and labeling before testing.
• Equilibrate foil pouches and specimens to room temperature before opening.
• Inoculate test cassettes with exact specimen volume, start timing, and read results strictly within the 3-minute to 10-minute window.
• Verify procedural control band validity before authorizing results in the LIS or issuing official reports.
• Communicate urgent positive results to emergency room or outpatient clinicians as required.

4.5 Laboratory Aides

• Bring sealed urine specimens from outpatient and emergency collection areas to the testing workstation.
• Restock clean urine collection containers and disposable transfer pipettes.
• Dispose of used cassettes and pipettes into yellow biohazard waste containers per hospital biosafety protocols.
• Do not perform tests, read test cassettes, interpret lines, or report pregnancy test results.

5.0 Policy / Procedure

5.1 Test Principle and Kit Specifications

` Abbott Bioline hCG Test Architecture | +---> Product: Abbott Bioline hCG (Cat. No. 30FK10) | Format: 25 Individually Foil-Pouched Cassettes per Kit | Storage: 1 to 30 °C (Do NOT Freeze) | Analytical Sensitivity: 25 mIU/mL in urine | +---> Analytical Specificity (Zero Cross-Reactivity): | Human Luteinizing Hormone (hLH): No cross-reactivity at 500 mIU/mL | Human Follicle-Stimulating Hormone (hFSH): No cross-reactivity at 1000 mIU/mL | Human Thyroid-Stimulating Hormone (hTSH): No cross-reactivity at 1000 µIU/mL | +---> Immunochromatographic Assay Mechanism: Urine applied to Specimen Well (S) migrates along nitrocellulose membrane Binds to monoclonal anti-beta-hCG colloidal gold conjugate Captured by immobilized anti-alpha-hCG antibody at Test Line (T) -> Red/Pink Band Excess conjugate captured at Control Line (C) by goat anti-mouse IgG -> Red/Pink Band `

The Abbott Bioline hCG test is a rapid, qualitative, one-step lateral-flow immunochromatographic immunoassay:

• When urine is added to the sample well (S), it dissolves the dried colloidal gold-labeled monoclonal anti-β-hCG antibody conjugate.
• If hCG is present at or above 25 mIU/mL, the resulting antigen-conjugate complex migrates by capillary action along the nitrocellulose membrane.
• The complex is captured by polyclonal anti-α-hCG antibodies immobilized in the Test (T) region, forming a visible pink/red band.
• Unbound gold conjugate continues migrating and is captured by goat anti-mouse antibodies immobilized in the Control (C) region, generating a mandatory pink/red control band.
• In the absence of hCG, only the C line forms.

5.2 Reagents and Materials Provided / Required

• Materials Provided (Abbott Bioline hCG, Cat. No. 30FK10): - Individually sealed foil pouches, each containing one test cassette and a desiccant packet. - Disposable plastic specimen droppers (calibrated to deliver approximately 30 to 35 µL per drop). - Package insert instructions.
• Materials Required But Not Provided: - Clean, dry, leak-proof plastic urine collection containers. - Calibrated digital laboratory stopwatch or timer. - Disposable gloves and personal protective equipment. - Clinical centrifuge (for turbid or hemolyzed specimens).

5.3 Storage and Stability

• Store unopened test kits at 1 to 30 °C in a dry environment out of direct sunlight. Do not freeze the test cassettes.
• Test cassettes remain stable until the expiration date printed on the sealed foil pouch.
• Do not open the foil pouch until ready to perform testing. The cassette must be used within one hour of opening to prevent humidity degradation.

5.4 Specimen Collection, Preparation, and Storage

• Specimen Type: Freshly voided human urine collected in a clean, dry container without chemical preservatives.
• Preferred Specimen: First-morning urine is strongly preferred. Overnight bladder concentration yields the highest specific gravity and peak β-hCG levels, enabling the earliest detection of pregnancy.
• Random Urine: Acceptable for urgent or emergency situations; however, very dilute urine (specific gravity < 1.005) may contain β-hCG concentrations below the 25 mIU/mL threshold during very early gestation.
• Turbid or Bloody Specimens: If urine is visibly cloudy, turbid with heavy amorphous precipitates, or tinged with blood, centrifuge 3 to 5 mL at 400 × g (approximately 1500 rpm) for 5 minutes. Use only the clear supernatant for testing. Particulate debris can clog the membrane pore matrix and cause false-positive streaking or test invalidation.
• Specimen Storage: Fresh urine should be tested within 2 hours of collection. If testing is delayed, urine may be refrigerated at 2 to 8 °C for up to 48 hours. Refrigerated urine must be equilibrated to room temperature (15 to 30 °C) and mixed thoroughly before testing.

5.5 Step-by-Step Analytical Procedure

` Step-by-Step Testing Sequence | +---> 1. Equilibrate pouch and urine to Room Temperature (15 to 30 °C) | +---> 2. Open foil pouch; place cassette on clean, flat horizontal surface | +---> 3. Label cassette with 2 unique Patient Identifiers | +---> 4. Hold dropper vertically; dispense exactly 3 DROPS (~100 µL) into Well (S) | +---> 5. Start calibrated timer immediately | +---> 6. Read analytical result at exactly 3 MINUTES | +---> 7. STRICT LIMIT: Do NOT read or interpret results after 10 MINUTES `

• Ensure the sealed foil pouch and urine specimen have reached room temperature (15 to 30 °C).
• Tear open the foil pouch at the notch, remove the cassette, and place it horizontally on a flat, clean, dry bench surface. Inspect the desiccant packet and discard; do not use the cassette if the desiccant indicates moisture exposure.
• Label the plastic casing of the cassette with two unique patient identifiers (Patient Name and Accession Number). Do not write on or touch the membrane reading window.
• Draw clear urine into the disposable plastic dropper provided in the pouch. Hold the dropper vertically above the circular sample well (S) at a 90° angle. Dispense exactly three (3) full drops (approximately 100 µL) of urine into the sample well (S), allowing each drop to absorb before adding the next. Ensure no air bubbles are expelled into the sample well, as trapped bubbles prevent smooth capillary wicking.
• Start the digital timer immediately upon adding the third drop of urine.
• Allow the test cassette to remain undisturbed on the flat bench during the incubation period. Observe the purple/pink chromatographic front moving across the result window.
• Read the test result at three (3) minutes.
• Do not read or interpret results after ten (10) minutes. As the membrane dries, non-specific protein binding and evaporation lines may develop in the test zone, producing false-positive artifacts.

5.6 Result Interpretation

• Positive Interpretation Note: Any visible pink or red line in the Test (T) region, regardless of how faint or weak its intensity, indicates a positive result, provided a distinct line is present in the Control (C) region. The shade or intensity of the T line does not quantify gestational age or hormone level.
• Invalid Protocol: If the Control (C) band does not appear at 3 minutes, the result is completely invalid. Never report an invalid test as negative. Discard the defective cassette, verify the lot expiry, and repeat the test immediately using a fresh cassette from an unopened pouch.

5.7 Quality Control

• Internal Procedural Control: Each Abbott Bioline hCG cassette contains a built-in internal procedural control. The appearance of the pink/red line in the Control (C) region confirms that adequate specimen volume was applied, proper membrane wicking occurred, and procedural technique was correct.
• External Quality Control: Positive and negative commercial or verified clinical urine controls shall be tested: - Upon receipt of each new shipment or lot number. - When storage temperatures deviate outside the 1 to 30 °C range. - Whenever test results appear clinically inconsistent or questionable. - Record external QC results in the electronic QC log under Quality Control Policy (registered under F-QM-002-B-V0).

5.8 Analytical Limitations and Clinical Cautions

• Very Early Gestation: In extremely early pregnancy (first several days following implantation), urinary hCG concentrations may be below the 25 mIU/mL cutoff. When clinical suspicion of pregnancy remains high despite a negative result, a fresh first-morning urine specimen shall be recollected and tested 48 to 72 hours later (urinary hCG typically doubles every 48 hours in early normal intrauterine pregnancy), or correlated with serum qualitative or quantitative β-hCG testing per Serum Qualitative Beta Hcg Pregnancy Test Sop.
• Dilute Urine Interference: Random urine with a low specific gravity (< 1.005) contains dilute hormone concentrations, which may cause false-negative results in early gestation. Recollect a first-morning clean-catch specimen.
• High-Dose Hook Effect: In rare pathological conditions involving exceptionally elevated hCG concentrations (> 500,000 mIU/mL), such as complete hydatidiform mole, choriocarcinoma, or multiple gestations, a false-negative result or paradoxical line weakening can occur due to the prozone hook effect. When gestational trophoblastic disease is clinically suspected, re-test the urine specimen diluted 1:10 and 1:100 in 0.85% physiological saline.
• Non-Pregnancy hCG Elevations: Elevated hCG levels may occur in non-pregnant conditions, including trophoblastic neoplasms, testicular germ cell tumors, ovarian teratomas, and certain gastrointestinal carcinomas. Post-menopausal women may exhibit physiologically elevated pituitary hCG (up to 10–15 mIU/mL), which typically does not exceed the 25 mIU/mL analytical cutoff.
• Spontaneous Abortion and Ectopic Pregnancy: Detectable levels of hCG persist in maternal circulation and urine for several weeks following spontaneous abortion, therapeutic termination, or postpartum delivery. An ectopic pregnancy may produce subnormal or slowly rising hCG concentrations.
• Evaporation Artifacts: Reading the cassette after 10 minutes carries a significant risk of viewing a non-specific grey or faint pink shadow in the test area caused by drying of the nitrocellulose matrix (evaporation line). Never interpret a line that appears after the 10-minute cutoff.

5.9 Result Reporting

• Results shall be authorized in the LIS or recorded on the official TCH Clinical Microscopy Report as: - Urine Pregnancy Test (Qualitative hCG): POSITIVE - Urine Pregnancy Test (Qualitative hCG): NEGATIVE
• Never report quantitative numbers or gestational age estimates from this qualitative rapid test.
• Document kit lot number, expiration date, and examining Medical Technologist signature.

6.0 Records

7.0 References

• DOH Clinical Laboratory QMS Tool, Section 3 — Service Delivery
• DOH Administrative Order No. 2021-0037, Annex B1 — Technical Standards for Clinical Laboratories
• ISO 15189:2022, Section 7.3 — Examination processes
• Abbott Bioline hCG Rapid Test Package Insert
• CLSI GP16-A3, Urinalysis — Approved Guideline

Companion policies:

• Scope of Service and Laboratory User Information Policy — Laboratory test menu and diagnostic scope of service
• LAB-QM-PRE-001 — Specimen collection, acceptance criteria, and rejection management
• Laboratory Reporting Policy — Result review, validation, and diagnostic report release