STD-test-accuracyThis question pops up in the mind, mostly after a casual sexual encounter (maybe with a stranger or a fling) or upon observing possible STD symptoms on your body. Getting tested for STD is always a best practice to gain the peace of mind, also, it is generally the most reliable way to know if you’ve contracted an STI or STD so that you can start your treatment (if infected).

 

But we question the accuracy of the STD test every time we are about to test for an STD or after getting the test results. How accurate is/was the test? The answer to this question is certainly more than 90% for most of the tests. Most of the testing centers these days adhere to the strict mandates laid by the HIPAA and are CLIA-certified and FDA-approved laboratory testing facilities. However, this alone is not full proof. There are many factors leading to the accuracy of any tests.

Lets us see which factors determine the accuracy of any STD test.

1. Sensitivity & Specificity of the test *
2. Positive Predictive Value (PPV) and Negative Predictive Value (NPV)*
3. STD window period (Incubation period of STD) *
4. Type of STD tests (RNA, antigen, culture test, etc) *

*  above explained in a detailed manner after the table

 

STD accuracy table

The following table indicates the type of test, the best time to get tested for accurate results along with their respective Sensitivity and Specificity.

STD	Type of Sample	Types of STD test	When to test (time span)	Sensitivity	Specificity
Chlamydia	Blood	Enzyme-linked immunosorbent assay (ELISA); Antibodies, IgM	1-5 days	85.70%	98.10%
	Blood	Enzyme immunoassay (EIA); Antibodies, IgG	6–12 weeks	97.80%	99.70%
	Urine	Cell Culture and Subsequent Detection of Chlamydia by Fluorescent Antibody Test Method	after 2 weeks	65.00%	99.60%
	Swab	Swab cultures	after 5 days	77%	99.00%
	Swab	Direct Fluorescent Antibody (DFA)	after 2 weeks	65%	99.60%
Gonorrhea	Blood	Enzyme-linked immunosorbent assay (ELISA); Antibodies, IgM	After 6 days	99%	98%
	Urine	Nucleic Acid Amplification (NAA)	After 2 weeks	97.60%	100%
	Swab/Blood	Gonorrhea swab cultures	after 3 days	95%	98%
	Swab	Gram Stain	after 96 hours	90%	98%
Herpes	Swab	Herpes viral culture	4 to 6 weeks	50%	100%
	Swab	Polymerase chain reaction (PCR) test	After 6 days	92.30%	97.50%
	Blood	Antibody tests	3 to 4 weeks	93%	95%
	Swab	Herpes virus antigen detection test	after 10 to 12 days	90%	98%
Syphilis	Blood	Venereal disease research laboratory (VDRL) test	3 to 5 weeks	50%	99.80%
	Blood	Rapid plasma reagin (RPR) test	4 weeks and later	52.50%	94.30%
	Blood	Rapid immunochromatographic test	after 3 to 4 weeks	84.10%	95.30%
	Blood	Enzyme immunoassay (EIA) test	after 2–3 weeks	82%	99%
	Blood/Spinal fluid	Fluorescent treponemal antibody absorption (FTA-ABS) test.	after 13 weeks	73%	100%
	Blood	Treponema pallidum particle agglutination assay (TPPA).	after 21 days	85%	98%
	Swab	Darkfield microscopy	after 9–90 days	79%	98%
	Blood	Microhemagglutination assay (MHA-TP).	3 weeks	68.50%	82.30%
Hepatitis B	Urine	HBsAg (hepatitis B surface antigen)	6 weeks	90%	99.50%
	blood	Anti-HBs or HBsAb (hepatitis B surface antibody)	7 weeks	88.80%	100%
	blood	Anti-HBc or HBcAb (hepatitis B core antibody)	7 weeks	90%	78.90%
Hepatitis C	Urine	HCV Antibody Testing	8 to 9 weeks	99%	99%
	blood	HCV Viral Load Testing	14 to 180 days	98%	99%
	Home Testing  kit	HCV Genotypic Test	7 to 8 weeks	99.50%	98.80%
HPV	Blood:DNA	Direct: Genome detection	after 3-5days	96%	85%
	Blood:DNA	Amplification	10 days	96%	33%
	Blood:DNA	Amplification and genotyping of HPV-16 and HPV-18	After 5 days	95.80%	88.90%
	Blood:RNA	Amplification of E6/E7 proteins	18 days	71.80%	58.30%
	Blood:RNA	Monoclonal antibodies	after 10 days	87%	100%
	Swab	PAP Smear	4 weeks to 8 months	92%	23%
Trichomonas	Urine / vaginal fluid	Urinalysis	5 to 28 days	82%	97%
	Rapid	Antigen (RADT)	13 days	68.20%	89.70%
	Blood	nucleic acid amplification	7 to 21 days.	96.00%	95.30%
HIV	RNA/DNA	PCR/Viral load	7 days	85.70%	98.10%
	Antigen	p24 only test (Ag)	2-8 weeks	58%	99.90%
	Antigen & antibody	4th generation Antigen and Antibody (Ag/Ab) tests	4 weeks	95%	99.78%
	Antibody	1st/2nd/3rd generation antibody only tests (ELISA,ELI, MEA/ELFA/ECLIA) includes OraQuick	18 to 45 days	88.20%	99.70%
	Antibody	Rapid tests: finger prick and oral swab test are antibodies only: includes OraQuick	2 to 4 weeks	75%	96%

Download this entire table in one sheet

Let’s see each factor determining the accuracy of any STD test in detail.

 

Download: STDcheck.com’s test result for your reference

 

Sensitivity & Specificity of the test 

 

Definition: Sensitivity is the ability of a test to identify patients that have the disease.

 

So if 10 people have a disease and eight of ten of those patients as being positive. Then those are true positives. Sensitivity then is 80%. Rest two of those patients, however, are going to be negative, even though they have the disease and those are called false negatives. 

So when a test that is highly sensitive is good for ruling out disease, when the test is negative (test result).

 

Definition: Specificity of the test, is its ability to identify those without the disease.

10 people don’t have any disease. So if 7 out of 10 patients have been tested negative because they don’t have the disease and it didn’t show in the test as well. So those are truly negative and the Specificity of the test is 70%. So, 3 of them have been indicated as positive, even though they don’t have the disease. Those are referred to as False positive.

So when the test is specific is good at ruling in the disease when test positive

 

Positive Predictive Value (PPV) and Negative Predictive Value (NPV)

Positive predictive value is the ability to detect the presence of disease. It measures the probability of having the disease when the test is positive. 

Negative predictive value is the probability of not having the disease when the test is negative.

Know in more depth: Sensitivity, Specificity, Positive and Negative Predictive value

STD test window period or the Best time to get tested for STD 

Some STDs take time to get detected in the clinical test. This is known as their Incubation period. STD testing window is the time between getting an STD and having it show up on a test. 

So if you get tested during this window, you may get a False Negative result thus hampering the accuracy of the test.

Know more in-depth: Best time to get tested for STD, STD testing window and Incubation period of STD.

 

Type of STD tests (RNA, antigen, culture test, etc) 

Different types of Tests have a different level of accuracy. This is because some STD tests look directly for the infecting bacteria, while others look out, indirectly, for the bacteria/virus presence.

Following are the types of test and the thing they look to detect bacterias/viruses

 

Urine test for STD

Urine testing is currently primarily used to detect bacterial STDs. Best fit for Chlamydia, Gonorrhea test. 

 

Bacterial culture test for STD (swab sample is preferred)

Bacteria culture test involves growing bacteria, this test is applicable to see if the patient has a bacterial infection. This test is more accurate than the Urine test as culture (test) can detect even very low numbers of bacteria, thus the sensitivity of this test is high. Thus asymptomatic Chlamydia and Gonorrhea can be detected using this test.

 

Antibodies/Antigen test (Blood test)

As the name suggests, this test does not identify the actual bacteria or virus, rather it looks out for immune proteins (called antibodies) that your body produces (to fight) in response to the infection. Herpes can be detected using an IgG antibody test. HIV,/Hepatitis can also be detected using the Antibody/Antigen test.

The difference is Antigens are molecules whereas Antibodies are proteins capable of stimulating the immune response.

 

Viral load test (HIV blood test)

This test is used to detect HIV, wherein the actual calibration of virus or amount of virus is calibrated in a given blood sample. 

 

Bacterial DNA/RNA test for STD

Instead of growing bacteria, these tests look for bacterial DNA in the sample. HIV RNA test detects the genetic material of the virus itself.

 

VDRL test (Blood test)

The Venereal disease research laboratory test is a blood test used to determine the presence of syphilis is blood.

 

Visual diagnosis

For STDs like HPV the visual test to detect genital warts is sufficient.

 

Review of some of the STD testing clinics 

STD Check

• Certification: FDA-approved laboratory tests and CLIA-certified
• Trusted Source
•  +4500 labs
• Tests for: Every STD: Chlamydia, gonorrhea, syphilis, hepatitis A, hepatitis B, hepatitis C, herpes simplex virus-1 and -2, HIV. (Covered in 10 test panel available at a discounted rate)
• Result turnaround time: 1 to 2 days
• Cost: $24 to $349
• Physician support included: Yes — phone consultation with a healthcare provider after a positive test result

Shop on STDcheck.com with $10 discount coupon inside 

Healthlabs.com

• Certification: CLIA-certified and FDA-approved laboratory 
• Tests for: Chlamydia, gonorrhea, hepatitis A, hepatitis B, hepatitis C, herpes simplex virus-1 and -2, HIV, syphilis, trichomoniasis
• Result turnaround time: 2 to 8 business days
• Cost: $52 to $198
• Physician support included: Yes — condition counseling and prescription when eligible

Healthlabs.com isn’t active in North Dakota, Rhode Island, New York, New Jersey, Maryland, and Hawaii.

Shop on Healthlabs.com

 

myLAB Box (testing from comforts of your home)

• Certification: FDA-approved laboratory tests and CLIA-certified
• Trusted Source
• Tests for: Chlamydia, gonorrhea, hepatitis B, hepatitis C, herpes simplex virus-1 and -2, HPV, HIV, mycoplasma, syphilis, trichomoniasis
• Result turnaround time: 2 to 8 days
• Cost: $79 to $369
• Physician support included: Yes — phone consultation with a healthcare provider after a positive test result

Shop on myLABBox.com.

Health Testing Center

• Certification: CLIA-certified and FDA-approved laboratory tests 
•  +3000 lab Network
• Tests for: Chlamydia, gonorrhea, hepatitis C, herpes simplex virus-2, HIV, HPV, mycoplasma, syphilis, trichomoniasis, ureaplasma
• Result turnaround time: 2 to 8 days
• Cost: $89 to $444
• Physician support included: No — 

Not currently available in 5 states: MA, MD, NJ, NY, and RI.

Shop on Healthtestingcenter.com