FAQ-2682
What is the threshold cycle or Ct value?
The Ct or threshold cycle value is the cycle number at which the fluorescence generated within a reaction crosses the fluorescence threshold, a fluorescent signal significantly above the background fluorescence. At the threshold cycle, a detectable amount of amplicon product has been generated during the early exponential phase of the reaction. The threshold cycle is inversely proportional to the original relative expression level of the gene of interest.
Related products
QuantiFast Pathogen +IC Kits
The QuantiFast Pathogen +IC Kits are designed for sensitive and rapid real-time PCR or one-step RT-PCR detection of pathogen nucleic acids using sequence-specific probes. To enable high process safety through correct interpretation of negative detection results, each kit contains reagents for multiplex real-time detection of up to 4 user-defined pathogen targets (e.g., virus, bacteria, fungi etc.) plus the Internal Control (IC). Two kit formats are available: The QuantiFast Pathogen RT-PCR +IC Kit for detection of viral RNA, which contains an internal RNA control template, plus the Internal Control primer/probe set, or the QuantiFast Pathogen PCR +IC Kit for detection of viral, bacterial, or fungal DNA, which contains an internal DNA control template, plus the Internal Control primer/probe set. With both kits, ROX is supplied in 2 tubes of different concentrations, enabling use on virtually any real-time instrument. For convenience, the master mix can be stored at 2–8°C.
RT2 SYBR® Green qPCR Mastermixes
RT2 SYBR Green qPCR Mastermixes are highly suited for real-time PCR applications using SYBR Green, and are required for guaranteed qPCR performance of the RT2 qPCR Primer Assays, RT2 Profiler PCR Arrays, RT2 lncRNA qPCR Assays, and RT2 lncRNA PCR Arrays. This Mastermix should be used in qPCR instruments under standard cycling conditions. RT2 SYBR Green qPCR Mastermixes are also suitable for use with EpiTect ChIP and EpiTect Methyl II qPCR Assays and PCR Arrays.
RT2 qPCR Primer Assays
RT² qPCR Primer Assays are specifically designed and experimentally verified for real-time PCR analysis. The rigorous assay verification criteria ensure PCR specificity and efficiency for reliable and accurate gene expression analysis results.
QuantiFast Multiplex PCR Kits
QuantiFast Multiplex PCR Kits enable fast and reliable quantification of up to 4 cDNA or gDNA targets in a single tube by multiplex, real-time PCR or two-step RT-PCR. Q-bond technology and an optimized master mix promote fast multiplex real-time PCR, not only on fast cyclers with short ramping times, but also on standard cyclers. The combination of a hot start and a unique PCR buffer system in the ready-to-use master mix ensures highly sensitive qPCR on any real-time cycler without the need for optimization. Two kit formats are available: the QuantiFast Multiplex PCR Kit for cyclers that require ROX dye for fluorescence normalization, and the QuantiFast Multiplex PCR +R Kit for all other cyclers. For convenience, the master mix can be stored at 2–8°C.
IMPORTANT NOTE: As announced earlier, the production of the QuantiFast kits has been discontinued since mid-2021. Hence, these products will be available only until stocks last. Visit the product page of the successor kit to view improved features or to request a trial kit.
For more information and FAQs on this transition, visit: www.qiagen.com/PCRresource.
QuantiTect Virus Kits
The QuantiTect Virus Kit is specially designed for highly sensitive detection of up to 4 viral nucleic acid targets by multiplex, real-time one-step RT-PCR using sequence-specific probes. Multiple viral RNA and/or DNA targets plus internal controls can be detected in a single tube without loss of sensitivity. The concentrated 5x master mix enables the addition of higher sample input and contains HotStarTaq Plus DNA Polymerase. The QuantiTect Virus RT Mix contains a unique formulation of Sensiscript Reverse Transcriptase that is optimized for highly sensitive detection of viral RNA. Two kit formats are available: the QuantiTect Virus Kit for cyclers that require ROX dye for fluorescence normalization and the QuantiTect Virus +ROX Vial Kit for other cyclers. For convenience, the master mix can be stored at 2–8°C.
QuantiFast Probe PCR Kits
QuantiFast Probe PCR Kits deliver fast and sensitive quantification of gDNA and cDNA targets by real-time PCR and two-step RT-PCR using sequence-specific probes. Q-bond technology and an optimized master mix enable shorter real-time PCR run times, not only on fast cyclers with short ramping times, but also on standard cyclers. The combination of a hot start and a unique PCR buffer system in the ready-to-use master mix ensures highly sensitive qPCR on any real-time cycler without the need for optimization. Two kit formats are available: the QuantiFast Probe PCR Kit for cyclers that require ROX dye for fluorescence normalization, and the QuantiFast Probe PCR +ROX Vial Kit for all other cyclers. For convenience, the master mix can be stored at 2–8°C.
IMPORTANT NOTE: As announced earlier, the production of the QuantiFast kits has been discontinued since mid-2021. Hence, these products will be available only until stocks last. Visit the product page of the successor kit to view improved features or to request a trial kit.
For more information and FAQs on this transition, visit: www.qiagen.com/PCRresource.
QuantiTect RT-PCR Kits
QuantiTect RT-PCR Kits enable sensitive quantification of RNA targets by real-time one-step PCR using sequence-specific probes or SYBR Green I detection. The kits also allow reliable quantification of up to 5 RNA targets in a single tube by multiplex, real-time one-step RT-PCR. The combination of a hot start and a unique PCR buffer system in the ready-to-use master mix ensures highly sensitive qRT-PCR on any real-time cycler without the need for optimization. The dNTP mix includes dUTP, allowing optional treatment with UNG. For convenience, the master mixes in QuantiTect one-step RT-PCR kits can be stored at 2–8°C. Two kit formats are available for multiplex RT-PCR using sequence-specific probes: the QuantiTect Multiplex RT-PCR Kit for cyclers that require ROX dye for fluorescence normalization, and the QuantiTect Multiplex RT-PCR NoROX Kit for all other cyclers. The QuantiTect SYBR Green RT-PCR Kit is supplied with an optimized RT mix for efficient and sensitive reverse transcription over a wide range of RNA template amounts.
QuantiTect Primer Assays
QuantiTect Primer Assays are genomewide, bioinformatically validated primer sets for use in SYBR Green-based real-time RT-PCR on any cycler. Assays are available for all genes from human, rat, mouse, and many other species. Each assay for a specific gene is supplied as a lyophilized mix of forward and reverse primers that can be easily reconstituted to obtain a 10x assay solution (reaction components for real-time RT-PCR need to be ordered separately). When used in combination with QuantiFast, QuantiTect, Rotor-Gene, or FastLane Kits for SYBR Green detection, QuantiTect Primer Assays guarantee highly specific and sensitive results in real-time RT-PCR that are comparable to probe-based detection.
QuantiTect Reverse Transcription Kit
The unique QuantiTect Reverse Transcription Kit provides a fast and convenient procedure for cDNA synthesis with integrated genomic DNA removal. Genomic DNA contamination in RNA samples is effectively eliminated by gDNA Wipeout Buffer. All components that are required for fast and efficient reverse transcription are provided with the QuantiTect Reverse Transcription Kit, including Quantiscript Reverse Transcriptase, Quantiscript RT Buffer, and a unique RT Primer Mix. The synthesized cDNA is optimized for use in real-time PCR, allowing reliable quantification of targets from all regions of mRNA transcripts.
QuantiTect PCR Kits
QuantiTect PCR Kits (qPCR kits) enable sensitive quantification of gDNA and cDNA targets by real-time PCR and two-step RT-PCR using sequence-specific probes or SYBR Green I detection. The real-time PCR kits also allow reliable quantification of up to 5 gDNA or cDNA targets in a single tube by multiplex, real-time PCR or two-step RT-PCR. The combination of a hot start and a unique PCR buffer system in the ready-to-use master mix ensures highly sensitive qPCR on any real-time cycler without the need for optimization. The dNTP mix includes dUTP, allowing optional treatment with UNG. For convenience, the master mixes in QuantiTect PCR Kits can be stored at 2–8°C. Two kit formats are available for multiplex PCR using sequence-specific probes: the QuantiTect Multiplex PCR Kit for cyclers that require ROX dye for fluorescence normalization, and the QuantiTect Multiplex PCR NoROX Kit for all other cyclers.