Comparative Evaluation of Lateral Flow and ELISA-Based FIV Antibody Kits in Routine Veterinary Screening

Introduction

Feline Immunodeficiency Virus (FIV) is a widely recognized retrovirus in domestic cats and free-ranging feline populations. It affects cat health by targeting immune cells, primarily CD4+ T lymphocytes, leading to increased risk of secondary infections. Early and accurate detection of FIV antibodies is necessary for maintaining proper feline group health, controlling spread in shelters, guiding individual care decisions, and identifying candidates for isolation.

Two of the most used diagnostic methods in veterinary labs and clinics are Lateral Flow Assays (LFAs) and Enzyme-Linked Immunosorbent Assays (ELISAs). While both serve the purpose of antibody detection, they differ in sensitivity, specificity, workflow, equipment requirements, and usability in field or laboratory settings. This comparative evaluation discusses their operational details, advantages, drawbacks, and utility in regular veterinary screening settings.

Background on FIV and Antibody Response

FIV is part of the Lentivirus genus in the Retroviridae family, similar in structure to other lentiviruses that affect mammals. It is transmitted through deep bite wounds, making outdoor male cats at higher risk (vet.cornell.edu).

After infection, cats generate detectable antibodies within 2–8 weeks, which remain for life (merckvetmanual.com). These antibodies become the primary diagnostic target. Diagnostic assays aim to detect FIV-specific IgG antibodies against viral core proteins such as p24, which is highly conserved across FIV subtypes (ncbi.nlm.nih.gov).

Diagnostic Methods Compared

1. Lateral Flow Assays (LFAs)

Lateral flow immunoassays, often used as point-of-care tests, operate on capillary action principles. They are designed with a test strip that contains immobilized FIV antigens and a detection conjugate (commonly colloidal gold or colored particles). When a sample is applied, any antibodies in the sample bind the antigen and migrate to form a visual line.

Main Features:

• Results available in ~10 minutes

• No lab instruments needed

• Stable at room temperature

• Small sample volume required (10–20 µL)

Sources:

• usda.gov

• fsis.usda.gov

• cfsph.iastate.edu

2. Enzyme-Linked Immunosorbent Assays (ELISAs)

ELISA platforms use microtiter plates coated with FIV antigens (usually recombinant p24). The assay involves multiple steps: sample incubation, washing, application of enzyme-labeled secondary antibody, substrate addition, and optical detection via a microplate reader.

Main Features:

• High sensitivity and specificity

• Amenable to batch testing

• Less subject to false results

• Suitable for confirmatory use

Sources:

• aphis.usda.gov

• nih.gov

• fda.gov

Laboratory Performance and Sensitivity

Several studies have examined the performance of LFA and ELISA kits for FIV screening.

• AAVLD-accredited laboratories across the United States confirm that ELISA tests consistently yield over 98% sensitivity and specificity across FIV subtypes (aavld.org).

• LFA test performance, on the other hand, has shown variable sensitivity from 83% to 95%, depending on batch and brand (onlinelibrary.wiley.com).

• LFAs are more prone to false negatives in early or late-stage infection and false positives in vaccinated cats, as they cannot differentiate natural from vaccine-induced antibodies (vetmed.iastate.edu).

A specific evaluation from ucdavis.edu reported that while LFAs provided quick results, their performance was inconsistent when compared to ELISA-based FIVCHECK Ab kits.

Real-World Veterinary Screening Workflow

Common Use Cases

Veterinary practitioners in field or mobile clinics often choose LFAs due to their simplicity. Shelters benefit from initial LFA screening followed by batch ELISA for any reactive or ambiguous cases (extension.missouri.edu).

Economic and Practical Factors

Cost Comparison

• LFAs: ~$10–15/test, includes everything in a disposable cassette

• ELISA: $5–10/test (bulk), but requires instruments ($1,000+ initial cost)

Storage and Shelf-Life

• LFAs: Stable at room temperature, 12–24 month shelf life

• ELISAs: Require refrigeration, multiple reagents, limited shelf life after opening

Time to Result

• LFAs: 10–15 minutes

• ELISA: 2–4 hours depending on batching and wash cycles

Regulatory and Certification Bodies

Reliable FIV kits are listed and evaluated by several agencies:

• USDA Center for Veterinary Biologics (aphis.usda.gov)

• FDA CVM product tracking database (fda.gov)

• National Animal Health Laboratory Network (nahln.org)

• World Organisation for Animal Health (WOAH) (woah.org)

These agencies oversee batch validation, performance documentation, and approval for market distribution.

Conclusion and Implementation Guide

Screening Strategy Recommendation

For veterinary clinics and animal shelters:

1. Use LFAs like SNAP FIV/FeLV Combo for rapid triage.

2. Confirm positive or unclear LFA results with ELISA-based FIVCHECK Ab ELISA or INgezim FIV.

3. Avoid relying on LFA only in high-stakes decisions (e.g., euthanasia or adoption denial).

4. Establish retesting timelines post-exposure (at least 8 weeks later).

5. For vaccinated cats, use ELISA platforms with confirmed non-reactivity to vaccine-induced antibodies (cdc.gov).

Final Notes

Accurate FIV diagnosis depends on appropriate test selection, timing of sample collection, and interpreting results in clinical context. While LFAs offer portability and speed, ELISA methods remain the standard for diagnostic depth and reliability.

Both technologies are useful tools—but in combination, they deliver best outcomes for feline care management.