The common types of ELISA all measure a binding event with an enzyme-linked readout, but the way each plate is built — what is coated, what binds what, and where the label sits — changes what the assay can actually measure. Choosing the wrong ELISA format is one of the most common reasons an assay fails to give a meaningful result. This guide walks through every format in the BioHippo ELISA kit collection and maps each to the target and sample it fits.
Types of ELISA: how the format decides the result
Every ELISA measures a binding event, but the plate architecture decides what it can see. A sandwich assay that needs two epitopes cannot measure a small hapten. An indirect assay built to titer antibodies will not quantify a cytokine. A standard-sensitivity kit reports “below detection” for an analyte that sits near baseline, collapsing the very biology you are trying to see. Matching the format to the analyte, the sample matrix, and the question is what turns a plate of wells into data.
BioHippo’s portfolio spans the full set of ELISA formats plus two dedicated performance lines: High-Sensitivity and QuickTest.
Choosing an ELISA format: start from three questions
Before comparing individual kits, three questions narrow the field to one or two formats. Work through them in order.
- Are you measuring an antigen, or an antibody? Quantifying a protein or antigen puts you in sandwich (large, multi-epitope targets) or competitive (small molecules, haptens) territory. Detecting or titering an antibody points to indirect or a capture variant.
- How big is the target, and can it present two epitopes? A protein large enough for two antibodies to bind at once can be sandwiched — the most specific, matrix-tolerant option. A small molecule, drug, hormone, or peptide with a single epitope cannot, so it is measured by competition.
- Where does the informative signal live, and how fast do you need it? If the analyte sits near baseline or the sample is scarce, step up to high-sensitivity. If you are screening many samples or need a same-day answer, a QuickTest or one-step format trades a little dynamic range for speed.
The four main types of ELISA: sandwich, competitive, indirect, direct
Almost every ELISA is a variation on four building blocks. Understanding these four core types makes the specialized formats that follow obvious.
Sandwich ELISA — quantifying a specific protein
A capture antibody is coated on the plate, the target antigen binds to it, and a second detection antibody against a different epitope completes the “sandwich,” carrying the enzyme label. Because two antibodies must both recognize the same molecule, specificity is high and the assay tolerates crude, complex matrices without prior purification. Use it to quantify a defined protein — cytokines, chemokines, growth factors, hormones, or disease biomarkers — in serum, plasma, lysate, or conditioned media, when the target is big enough to present two non-overlapping epitopes.
Competitive ELISA — small molecules and haptens
In a competitive ELISA, sample antigen competes with a fixed amount of labeled antigen for a limited quantity of antibody, so signal is inversely proportional to concentration. Only one antibody and one epitope are required, which is why this is the format of choice for molecules too small to sandwich — a drug, steroid or thyroid hormone, mycotoxin, antibiotic residue, or short peptide. Example BioHippo competitive ELISA kits:
- Human Cortisol ELISA Kit (steroid hormone) · BHE10501955
- Human Testosterone (T) ELISA Kit (steroid hormone) · BHE10504528
- Human Estradiol (E2) ELISA Kit (steroid hormone) · BHE10502311
Indirect ELISA — detecting and titering antibodies
Antigen is coated on the plate; a primary antibody from the sample binds it; an enzyme-conjugated secondary antibody then detects the primary. Several labeled secondaries bind each primary, so signal is amplified and sensitivity is high, and one universal secondary serves many primaries. Use an indirect ELISA to measure an antibody response: vaccine seroconversion, infection serology, antibody titer, or screening antisera and hybridoma supernatants. Example BioHippo indirect (IgG serology) ELISA kits:
- Human Herpes Simplex Virus I+II antibody (IgG) ELISA Kit · BHE10502709
- Human anti-Toxoplasma antibody (IgG) ELISA Kit · BHE10501374
- Human anti-Rubella Virus (RV) antibody (IgG) ELISA Kit · BHE10501344
Direct ELISA — fast check of an abundant antigen
The sample antigen is coated directly on the plate and detected by a single enzyme-conjugated primary antibody, with no secondary. This is the shortest protocol with the fewest wash steps and no risk of secondary cross-reactivity, at the cost of lower sensitivity and less flexibility, since every primary must be individually labeled. Use a direct ELISA when the antigen is abundant and relatively pure and you want a quick check with a directly conjugated antibody.
Specialized ELISA formats: one-step, capture, and bridging ELISA
Beyond the four base chemistries, several variants exist for particular sample types and questions.
One-step (single-step) sandwich ELISA
Sample and detection antibody are added together and incubated in a single step, cutting one incubation and wash cycle versus the classic two-step sandwich. It keeps sandwich specificity while shortening time-to-result, with the caveat that very high analyte concentrations can produce a “hook” effect if samples are not appropriately diluted.
Capture (antibody-capture) ELISA — isotype-specific detection
A capture ELISA coats an anti-immunoglobulin (for example anti-IgM) to pull a particular antibody class out of the sample before antigen and label are applied. Where indirect ELISA captures the sample antibody by specificity (coating the antigen), capture ELISA captures by class (coating an anti-isotype antibody), then adds labeled antigen to probe which of those antibodies are specific — the two steps run in reverse order. That is why capture is preferred for IgM detection in acute infection: grabbing the IgM first avoids competition from far more abundant IgG and suppresses rheumatoid-factor false positives. Example BioHippo capture (IgM) ELISA kits:
- Human anti-Cytomegalovirus (CMV) antibody (IgM) ELISA Kit · BHE10501249
- Human Chlamydia pneumoniae (Cpn) antibody (IgM) ELISA Kit · BHE10501768
- Human EchoVirus (ECHO) antibody (IgM) ELISA Kit · BHE10502199
Bridging ELISA — anti-drug antibodies and immunogenicity
A bridging ELISA measures an anti-drug antibody (ADA) by sandwiching it between two copies of the drug: the plate is pre-coated with the drug, the serum sample’s anti-drug antibody grabs it with one arm, and an HRP-labeled copy of the same drug binds the other arm to complete the “bridge,” read at 450 nm. Because both sides are the same drug, a single kit works regardless of the antibody’s species or isotype — the standard format for immunogenicity testing. BioHippo lists this on product pages as “Sandwich ELISA, double antigen.” Example BioHippo bridging (ADA) ELISA kits:
- Human Anti-Adalimumab (Humira) antibody ELISA Kit · BHE10809839
- Anti-Infliximab (Remicade) antibody ELISA Kit · BHE10809997
- Human anti-Bevacizumab (Avastin) antibody ELISA Kit · BHE10809665
Qualitative vs. quantitative kits
Every BioHippo kit is designated either qualitative (a positive/negative call, ideal for pathogen or contaminant screening) or quantitative (a concentration read against a standard curve), shown in the kit’s Assay Type field on the product page. In practice it follows the format and target: sandwich and competitive kits are typically quantitative, while many pathogen-serology (indirect and IgM-capture) kits are qualitative. Confirm which a given kit provides by checking its Assay Type.
Sandwich vs. indirect vs. competitive ELISA: a quick comparison
The direct vs. indirect ELISA question, and sandwich vs. competitive, both come down to what is coated and how signal tracks concentration. This table sets the four base formats side by side.
| Format | What it measures | Antibodies / epitopes | Signal vs. concentration | Typical use |
|---|---|---|---|---|
| Sandwich | Antigen (protein) | Two antibodies, two epitopes | Proportional | Cytokines, biomarkers in serum, plasma, lysate |
| Indirect | Antibody | Coated antigen + labeled secondary | Proportional | Serology, vaccine titer |
| Competitive | Small molecule / hapten | One antibody, one epitope | Inverse | Steroids, drugs, mycotoxins |
| Direct | Antigen (abundant) | One labeled primary | Proportional | Quick expression or coating check |
High-sensitivity and QuickTest ELISA kits
Two BioHippo collections address the two most common reasons a standard kit falls short: the signal is too faint, or the timeline is too tight.
High-Sensitivity ELISA. Enhanced detection chemistry pushes the lower limit of detection well below a standard kit, resolving analytes that would otherwise read as “undetectable.” Reach for it when the analyte sits near baseline, when sample volume is constrained (scarce serum, small-volume CSF, microdialysate, low-yield conditioned media), when the meaningful signal is at the low end (for example cardiac troponin), or when tracking small changes over time. If your samples read comfortably in the middle of a standard curve, a standard ELISA gives the same answer at lower cost with a wider working range. Browse the high-sensitivity ELISA kit collection or read the full high-sensitivity selection guide.
QuickTest ELISA. Streamlined, shortened protocols (often one-step) cut total assay time for faster turnaround, trading some dynamic range for speed — useful when screening large numbers of samples or when you need a same-day answer. Browse QuickTest ELISA kits.
DIY / matched antibody pairs. Validated capture and detection antibody pairs let you build and optimize your own sandwich assay, choosing your own plate, coating conditions, and buffers — the most flexible and, at volume, most economical route for custom, multiplexed, or automated assays.
ELISA format decision matrix: situation to recommended kit
| If your situation is… | Reach for | Why |
|---|---|---|
| Quantify a specific protein (cytokine, hormone, biomarker) in serum, plasma, lysate, or media | Sandwich ELISA | Two-antibody specificity, tolerates complex matrices |
| Same target, higher throughput or tight timeline | One-Step Sandwich / QuickTest | Fewer incubations, faster turnaround |
| Measure a small molecule or hapten (drug, steroid, mycotoxin, antibiotic) | Competitive ELISA | Works with a single epitope and one antibody |
| Detect or titer antibodies against an antigen (serology, vaccine response) | Indirect ELISA | Amplified signal, one secondary serves many primaries |
| Detect a specific antibody isotype (for example IgM in acute infection) | Capture ELISA | Isolates the isotype of interest |
| Screen for anti-drug antibodies / immunogenicity across species | Bridging ELISA | Species- and isotype-independent |
| Fast, simple check of an abundant, relatively pure antigen | Direct ELISA | Fewest steps, no secondary needed |
| Analyte near baseline, or sample volume is scarce | High-Sensitivity ELISA | Lower detection limit resolves faint signal |
| Building a custom, multiplex, or automated assay at scale | DIY / Antibody Pairs | Full control of format and per-well cost |
FAQ: selecting an ELISA format
What are the main types of ELISA?
The four base types of ELISA are sandwich, competitive, indirect, and direct. Sandwich quantifies proteins with two antibodies; competitive measures small molecules with one antibody and an inverse signal; indirect detects and titers antibodies; direct gives a fast readout of an abundant antigen. Specialized variants (one-step, capture, and bridging ELISA) and performance lines (high-sensitivity, QuickTest) build on these four.
What is the difference between direct and indirect ELISA?
Both coat the antigen, but direct ELISA detects it with a single enzyme-labeled primary antibody, while indirect ELISA adds an enzyme-labeled secondary antibody against the primary. The secondary amplifies signal and lets one universal secondary serve many primaries, so indirect is more sensitive and flexible; direct is faster with fewer steps and no secondary cross-reactivity.
How do I choose between sandwich and competitive ELISA?
It comes down to target size. A sandwich assay needs the antigen to present two separate epitopes so capture and detection antibodies can bind simultaneously — ideal for proteins. Small molecules and haptens (drugs, steroids, mycotoxins, short peptides) are too small for that, so they are measured by competition, where the analyte competes with a labeled antigen for a single antibody. Competitive is also the practical choice when you only have one good antibody.
What is a bridging ELISA used for?
A bridging ELISA detects anti-drug antibodies (ADA) in biotherapeutic immunogenicity studies. The anti-drug antibody is captured between a plate-bound copy of the drug and a labeled copy of the same drug, so one kit works regardless of the antibody’s species or isotype.
When is a high-sensitivity kit worth the extra cost?
When the biology lives at the bottom of the curve. If a standard kit reports many samples as “below detection,” or your sample volume is too small to concentrate, or you are tracking small changes at low concentration, a high-sensitivity kit resolves signal a standard assay cannot. If your samples already read in the middle of a standard curve, stay with the standard kit for the same answer at lower cost and a wider working range.
Do I need a quantitative kit, or is qualitative enough?
If the decision is present or absent (screening for a pathogen, contaminant, or seropositivity), a qualitative kit is faster and sufficient. If you need to compare levels between samples, track change over time, or build a dose–response, choose a quantitative kit that reads concentration against a standard curve.
References and resources
- BioHippo Application Note. High-Sensitivity ELISA Kit: When Sensitivity Changes the Result.
- BioHippo. ELISA Kits — full catalog and assay formats.
- BioHippo. QuickTest ELISA Kits.
Format descriptions summarize standard ELISA methodology and BioHippo product-line positioning. Confirm the assay format, sensitivity, sample compatibility, and intended-use statement on each product page before purchase.
