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http://www.badbugs.org/parasite/bh_lab_testing.htm

 

 

Quick links:

Optimal testing for parasites

Problems of intermittent shedding

Rectal swabbing (anoscopy)

Testing after treatment

Misreporting by laboratories

How to increase the chances of detection

Travel

 

Blasto's ability to cause symptoms has been under question by the

medical profession since its discovery in the early 1900s. Patients

are often advised that this bug does not cause symptoms. (see

medically documented symptoms of infection with Blastocystis hominis):

 

" I have tested positive for blastocytis hominis and am very sick at

the moment. My Dr. says it is not likely to be from this parasite

because it is non pathogenic. "

(sent by MS, March 03. More examples under Medical Mismanagement here)

 

Blastocystis hominis may be the most common parasitic infection of

humans. This organism is often missed on stool examination but grows

luxuriantly in all the media used to cultivate xenic Entamoeba.

Establishing Cultures of Entamoeba in vitro

London School of Hygiene & Tropical Medicine 2000

As B.hominis is the most common faecal parasite seen at both

Aberystwyth PHL and Swansea PHL in the UK, we feel that the CDSC

figures do not reflect the true incidence of B.hominis in England and

Wales. Indeed, all 139 reports of B. hominis reported to CDSC Wales in

2000 were detected by our two laboratories (unpublished data). We

believe that this can be attributed to laboratory awareness and the

use of suitable methodologies.

JJ Windsor, et al

British Journal of Biomedical Science 2001; 58: 129-130

 

A large study carried out in 2001 in the UK found the incidence of

Blasto. was more than 40% in those diagnosed with Irritable Bowel

Syndrome. (unpublished data).

 

Optimal testing for Blastocystis hominis

 

Medical literature shows that detection of Blastocystis hominis

increases significantly when three fecal samples, collected in jars

which contain liquid fixative. According to medical literature three

samples are 70% - 83% accurate. The fixative prevents morphological

changes once the parasite leaves it's host. These changes can render

the parasite unrecognisable by the the lab, resulting in a false-negative.

 

Accurate identification of Blastocystis hominis requires special

laboratory staining methods. These stains are not routinely used by

Australian or UK laboratories:

Over a one-year period, 1390 faecal samples were submitted to

Aberystwyth Public Health Laboratory for routine microbiological

examination. All were stained using a commercial trichrome method.

Blastocystis hominis was detected in 96 (6.9%), making it the most

common parasite found in the study. Of the B. hominis-positive

specimens, 73% were missed on direct microscopy. Molecular typing of

B. hominis has revealed extensive genetic diversity in morphologically

identical strains and thus detection by microscopy alone may not be

sufficient to confirm the role of this organism in human disease.

Br J Biomed Sci 2002;59(3):154-7

Incidence of Blastocystis hominis in faecal samples submitted for

routine microbiological analysis. Windsor JJ, Macfarlane L,

Hughes-Thapa G, Jones SK, Whiteside TM.

Participating and referee laboratories failed to authenticate

Blastocystis hominis as the correct answer (86 and 80%) so all answers

were accepted. Quality control examination of 4% of this sample showed

one cyst per every 3-5 oil fields. Staining quality was variable which

may have led to the high number of labs reporting " No Parasites Seen " .

NEW YORK STATE PARASITOLOGY PROFICIENCY TESTING PROGRAM 07 OCTOBER 2002

NYS Dept of Health.

" I sent stool samples to Quest Diagnostics (a huge laboratory chain

in the US that most medical doctors use) and to Dr. Amin**, samples

taken from THE SAME BOWEL MOVEMENTS and Dr. Amin found blasto and

Quest found nothing "

e-mailed by L., 21 Oct 2002

**Dr Amin is a parasitologist based at Parasitology Center Inc. in

Arizona USA.

 

Many people with parasitic infections have to rely on expensive

testing with private laboratories who specialise in testing for

Blastocystis hominis and Dientamoeba fragilis:

 

" I had to pay £225 to have my tests done. That's a lot of money "

E. (UK resident) tested by a private lab.

received 19 June 03 .

 

Although the results of three fixed samples, tested by an experienced

lab., is more reliable than results of a single sample tested by an

inexperienced lab, there are other important factors which result

often contributes to misdiagnoses:

Intermittent shedding (see below) of the parasite in fecal samples and

misreporting by labs.

 

The problems of intermittent shedding

 

As well as not always being present in fecal samples, the number of

parasites present in fecal samples fluctuates widely on a daily basis.

On some days the number of parasites excreted in feces may be too low

for detection by lab technicians. Many of those with Blasto. who

contact this site, as well as the author of this site, have

experienced alternating negative and positive results due to

intermittent shedding.

 

" I have been tested for parasites several times,

but it was yesterday that they came up with the diagnoses:

Blastocystis hominis. "

A.M., 7 May 2002

 

" I have just got my stool tests back which showed that I am still

infected with D.fragilis and interestingly this test also showed

B.hominis. I must point out that I took a laxative called picosulphate

to do purged samples to enhance the effectiveness of the tests. Seems

to have worked. "

M. October 2003

(submitting purged samples helps increase detection - info. here)

The shedding pattern of the vacuolar and cystic forms of Blastocystis

hominis in infected individuals have been shown in the present study

to be irregular.

The study shows that there is marked fluctuation in the shedding of

the parasite from day to day, varying from as high as 17 to 0 per x40

microscopic field.

The cystic stages when estimated in 8 Blastocystis-infected

individuals ranged from as high as 7.4x10(5) cysts per gram of stool to 0.

The shedding of cystic and vacuolar forms observed over a period of 20

days in experimentally-infected Wistar rats were not only shown to be

irregular but the amount varied from host to host. The study has

important diagnostic implications in that the stool samples must be

collected more than once from patients showing clinical signs and

symptoms to eliminate the cause of it to Blastocystis. The study also

shows that there are asymptomatic individuals who pass a large amount

of cysts as such individuals should be treated to prevent transmission

to others.

Irregular shedding of Blastocystis hominis.

Parasitol Res 1999 Feb;85(2):162-4

Vennila GD, et al

Occasionally the patient showed alternatively positive and negative

results in stool examinations.

Clinical significance of B.hominis infection

Am.J of Gastro. 1989

 

see " Medical Misdiagnoses " for more examples of intermittent shedding.

 

Because the diagnosis of Blastocystis hominis is made by microscopic

observation of the parasite in stool samples, intermittent shedding of

parasites is a problem not easily overcome except by testing 10 stool

samples. This is not an option for the majority of those with

parasitic infections:

Three samples is diagnostic 70-83% of the time. Ten samples is 90-100%

diagnostic. (Kean & Malloch, 1966).

 

Rectal Swabbing (Anoscopy)

 

Another method of parasite detection is, anoscopy or rectal swabbing.

This technique involves scraping inside the rectum area with a small

brush, preserving the contents in liquid fixative, and sending the

samples to a reputable laboratory for testing.

 

Anoscopy is claimed by doctors who use it to be far superior in the

detection of Blastocystis hominis when combined with stool sampling.

The number of doctors who use this method are few and it's

effectiveness as a technique for diagnosing parasites is generally

disputed by medical experts. However, there have been a number of

reports to this site of people who tested positive to Blastocystis

hominis and other parasites only by this method:

 

Karen was tested by Great Smokies Diagnostics (a reputable private

lab) and by her doctor's local lab. All samples were negative. She wrote:

" I have yet to find a parasite with a purged stool sample sent to

Great Smokies yet the rectal swabs have found it 5 times. "

Karen was retested a number of times due to failure of a number of

drug treatments to relieve her symptoms.

Susan was diagnosed with Blasto. cysts via anoscopy:

" I'm just wondering why the GS parasite test I did showed no

parasites, yet the rectal swab I had done through the doctor in NYC

did show the cysts. " (Feb. 2003)

Mary wrote:

" Found blasto. & giardia with an anoscopy in cyst form. I am convinced

this is the only valid test for a parasite. Worked for me twice now,

when other tests have shown nothing. "

 

Michael's results from Great Smokies Diagnostics and purged samples

submitted to Chelsea Biologics were negative for parasites. Anoscopy

samples tested by Great Smokies Diagnostics result:

Blastocystic Hominis --- Cysts Found 2+

(April 2003) G. was diagnosed with E.histolytica & giardia by rectal

swab after negative stool tests:

" I have been suffering for more than 20 years. I was diagnosed by a

doctor in New York City, Dr. Louis Parish. He and another doctor had

developed a test called a rectal swab. There was a lab tech in the

office that looked at the specimen right then and there. He had found

Giardia lambia and E. histolytica.

(Dec 2000)

 

Testing after treatment:

 

Drug treatment often knocks down the parsasites to a level too low for

detection. This problem was highlighted in a placebo controlled study

( Nigro L. et al. April 2003). Subjects with Blastocystis hominis were

treated with metronidazole. Twenty percent of the metro. treated

subjects were B. hominis positive one month after treatment. At six

months this figure had risen to 53%. The authors considered

reinfection may be a factor, but unlikely to be the sole reason for

Blasto's reappearance.

 

The author of this site experienced false negatives due to

intermittent shedding. After testing positive for D.fragilis 1994,

many samples tested between 1994 and 2001 were negative for

D.fragilis. In 2001 three fixed samples tested by a parasitologist

revealed not only D.fragilis but also Blasto. After taking Iodoquinol

and doxycycline to treat the D.fragilis three fixed samples were again

negative for both parasites. Approximately three weeks later three

purged samples were submitted. Blasto. showed up but D.fragilis did not.

 

Laboratories and misreporting

 

Because of Blasto's status as a questionable pathogen the presence of

Blasto. in stool samples is not always reported:

 

S., a Blasto. sufferer, asked the lab. technician of a large Canadian

hospital if they regularly find Blasto: " she replied that probably

more than 10-20% of the stool samples contain this parasite but that

they have only started to report the results since last year! "

e-mailed by S. 5 August 02

 

M. tested positive five times for Blasto. in recent years by a lab in

Brisbane, Australia. They confided that the opposition path. lab "

does not even mention Blasto. to the referring doctor when they find

it as they class it non important. " Her positive test was not much

help to M. as her doctors do not believe the Blasto. is the cause of

her symptoms of bloating, fatigue, nausea and irritable bowel. Her

physician considered her symptoms resulted from depression and a

anxiety disorder. She was prescribed anti-depressants meds.

 

R. is a Canadian infected ith the parasite Entamoeba histolytica. In

November 2003 he contacted the author of this site:

" I won't bore you with all the flagyl misadventures, which are very

similar to the stories already on your site. I was treated with the

stuff for entamoeba hystolica three times with no success before I

found a new doctor who followed the course with 20 days of yodoxin

(diodoquin in Canada). Test results finally came back neg for EH. Much

rejoicing, until the nurse mentioned, just by the way, there were some

other things found that are no considered pathogenic. Suspicious as I

was by this point, I asked him for the names of the other things

found. This was the first time I had ever heard of blastocystis, and

this was a year into my treatment! "

 

Failure to report the presence of Blasto. was documented by the

Canadian Centre for Disease Control in 2001:

 

Not all laboratories routinely searched for B. hominis. The provincial

reference laboratory for parasites reported all parasites found in the

samples. In only two of the seven other laboratories was this also

done. The five remaining laboratories (involving samples from seven

day-care individuals) later stated that they did not actively search

for, or report, B. hominis as a matter of course because it was not

believed to be pathogenic.

BLASTOCYSTIS HOMINIS: A NEW PATHOGEN IN DAY-CARE CENTRES?

Canada Communicable Disease Report - Volume 27-09, 1 May 2001

 

Your tests

 

If you haven't already done so, ask your doctor to test you for

parasites using three samples preserved in liquid fixative. If your

doctor will not agree, the labs listed on the help page utilise the

specific stool collection and testing methods necessary to detect both

Blasto. and D.fragilis. If you are having problems contact the author

of this site for further advice.

 

NOTE: Parasites adhere to the bowel. Taking a special laxative helps

to force the parasites out of the bowel and increases the detection

rate. Purging info. is available here

 

(more info. on testing for parasites is also available on the

D.fragilis section of the site)

 

TRAVEL & PARASITES:

" It was not necessary to travel to acquire the organism. "

Epidemiology & Pathogenicity of Blastocystis hominis, J.Clin. Micro.

by Doyle et al in 1989

 

Parasites are often not considered unless there is a history of travel

to tropical or developing countries.

 

" Doctors always ask if you have been out of the U.S., and if you

haven't they don't think you can have anything. "

e-mailed by D. (2002)

(for more examples see " Medical Mismanagement "