Performance of three enzyme immunoassays and two direct fluorescence assays for detection of Giardia lamblia in stool specimens preserved in ECOFIX

ECOFIX is a single-vial stool preservative that is both formalin- and mercury-free. We evaluated the abilities of three commercial Giardia lamblia-specific enzyme immunoassays (EIAs) (ProSpecT Giardia Microplate Assay [Alexon-Trend Inc.], Giardia Test [Techlab], and Premier Giardia lamblia [Meridian Diagnostics, Inc.]) and two commercial direct fluorescent-antibody (FA) assays for G. lamblia (Crypto/Giardia IF Test [Techlab] and Merifluor Cryptosporidium/Giardia [Meridian Diagnostics, Inc.]) to detect G. lamblia in 34 G. lamblia-positive and 44 G. lamblia-negative stool specimens (determined by traditional examination for ova and parasites) preserved in ECOFIX compared to their abilities to detect G. lamblia in the same specimens preserved in formalin as the "gold standard" for each assay. Of the 34 formalin-fixed positive specimens, the number detected by each assay was as follows:, Alexon EIA, 34; Meridian EIA, 27; Techlab EIA, 29; Meridian FA assay, 31; and Techlab FA assay, 28. Both FA tests and the Alexon EIA performed well with ECOFIX, but the other two EIAs detected fewer positive specimens (the difference was statistically significant with the Techlab EIA) when ECOFIX was the preservative. Use of G. lamblia cyst antigen from cultured organisms preserved in formalin and ECOFIX demonstrated that the Alexon EIA could detect smaller amounts of antigen in ECOFIX than the other two EIAs could and suggested that cyst antigen is more stable in formalin. We recommend that laboratories use an FA assay or the Alexon EIA if they plan to use ECOFIX as their stool preservative.     

Comparison of conventional stool concentration and preserved-smear methods with Merifluor Cryptosporidium/Giardia Direct Immunofluorescence Assay and ProSpecT Giardia EZ Microplate Assay for detection of Giardia lamblia.

Giardiasis is the most common parasitic infection in the United States. Variation in the numbers of cysts and/or trophozoites that are present along with the need for a skilled microscopist offer challenges in diagnosis. We compared the sediment wet preparation and permanent stained smear results (concentration in formalin-ethyl acetate and preparation of a smear prepared from a polyvinyl alcohol-preserved specimen) from 512 consecutive specimens with the results obtained by using the Merifluor Cryptosporidium/Giardia Direct Immunofluorescence Assay (DFA; Meridian Diagnostics, Inc., Cincinnati, Ohio) and the ProSpecT Giardia EZ Microplate Assay (EIA; Alexon, Inc., Sunnyvale, Calif.). The Merifluor DFA detected 33 of 33 positive specimens, and the ProSpecT EIA detected 32 of 33 positive specimens. The diagnostic sensitivities of the Merifluor DFA and the ProSpecT EIA were 100 and 97%, respectively. The specificities of the assays were 99.8%. The Merifluor DFA and the ProSpecT EIA appear to be equally sensitive, and both are more sensitive than conventional microscopy.     

Evaluation of three commercial assays for detection of Giardia and Cryptosporidium organisms in fecal specimens

There is an increasing demand for diagnostic testing for Giardia intestinalis (G. lamblia) and Cryptosporidium parvum, with a priority being placed on obtaining diagnostic results in an efficient and timely manner. Several commercial companies have developed rapid diagnostic tests that are simple to perform and can be completed in less time than traditional methods for detecting Giardia and Cryptosporidium: We compared one of these rapid tests, the ImmunoCard STAT! (Meridian Bioscience, Inc.) lateral-flow immunoassay, with the MERIFLUOR direct fluorescent-antibody (DFA) test, the ProSpecT EZ microplate assay for Giardia and the ProSpecT microplate assay for Cryptosporidium, and modified Kinyoun's acid-fast stained smears for the detection of Cryptosporidium using 246 specimens. The MERIFLUOR DFA (Meridian Bioscience, Inc.) test detected the largest number of cases (32 Giardia and 37 Cryptosporidium) infections and was used to calculate the sensitivity and specificity of the other tests. For Giardia, the sensitivities of the ImmunoCard STAT! and the ProSpecT Giardia EZ microplate assay (Alexon-Trend, Inc.) were 81 and 91%, respectively. For detection of Cryptosporidium, the sensitivities of the ImmunoCard STAT!, the ProSpecT Cryptosporidium microplate assay (Alexon-Trend, Inc.), and modified Kinyoun's acid-fast stained smears were 68, 70, and 78%, respectively. Test specificities were equal to or greater than 99%. Specimens with very small numbers of organisms were not detected by the ImmunoCard STAT!, the ProSpecT microplate assay or modified Kinyoun's acid-fast stained smears.     

Evaluation of rapid commercial enzyme immunoassay for detection of Giardia lamblia in formalin-preserved stool specimens.

Two hundred twenty-three formalin-preserved stool specimens were evaluated by using ProSpecT Giardia Rapid Assay (membrane bound) (Alexon, Inc., Sunnyvale, Calif.). Enzyme immunoassay (EIA) results were compared with those by conventional microscopic examination. Two hundred four specimens were negative by both methods, and 13 (6.3%) were positive. Five specimens were negative by initial microscopic exam and positive by EIA; three of these specimens were found to be positive upon extensive microscopic reexamination. The remaining two specimens were from patients who previously tested positive and who had recurrent symptoms of or responded to therapy for giardia. Therefore, we consider both cases to be true positives. One specimen exhibited a single cyst by microscopic exam and was negative by EIA Resolved results yielded a relative sensitivity of 95%, a relative specificity of 100%, a positive predictive value of 99.6%, and a negative predictive value of 100%, compared with a sensitivity of 74% for conventional microscopy.     

Comparison of four different methods for detection of Cryptosporidium species.

Newly available assays offer alternatives to conventional microscopic examination for Cryptosporidium spp. We compared two enzyme immunoassays, ProSpect Cryptosporidium microtiter assay (Alexon, Inc., Mountain View, Calif.) and Color Vue Cryptosporidium assay (Serady, Indianapolis, Ind.), and a direct immunofluorescent assay, Merifluor Cryptosporidium kit (Meridian Diagnostics, Cincinnati, Ohio), with acid-fast Kinyoun-staining for the detection of Cryptosporidium spp. Examinations were performed on 129 stool specimens received from patients during a recent waterborne outbreak. A specimen was considered positive when organisms could be identified visually by acid-fast and immunofluorescent stains or if organisms could be visualized by either acid-fast or immunofluorescent stain and detected by both enzyme immunoassays. The final number of positive specimens was 55. No single procedure detected all 55 positive specimens. Of these, ProSpect and Color Vue detected 52 (sensitivity, 94.5%), and the Kinyoun stain and Merifluor detected 53 (sensitivity, 96.4%). The final number of negative specimens was 74. One false-positive result was seen with both the Kinyoun stain and the ProSpect assay. The Color Vue and ProSpect assays required the most hands-on technologist time. The ProSpect assay and Merifluor kit were easiest to perform. The acid-fast stain was difficult to interpret. The Merifluor kit was easiest to read and was adaptable to both batch and single testing. Overall, the Kinyoun stain and the Merifluor test were preferable to both of the enzyme immunoassays because of the high reagent cost and hands-on time required for the enzyme immunoassays. The difficult interpretation of the Kinyoun stain smears made the Merifluor a more desirable test despite its higher cost.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of two commercially available enzyme immunoassays for detection of Clostridium difficile in stool specimens.

Clostridium difficile is the cause of most cases of pseudomembranous colitis, the most severe form of antibiotic-associated diarrhea. Rapid diagnosis guides both the treatment and the control of nosocomial spread of infection. Two enzyme immunoassay (EIA) kits developed for the rapid detection of C. difficile toxin A in fecal specimens, Premier (Meridian Diagnostics, Cincinnati, Ohio) and Tox-A test (TechLab, Virginia Polytechnic Institute Research Park, Blacksburg), were evaluated by using 410 fecal specimens. Seventy-six specimens were positive for C. difficile toxin B by the cytotoxin assay (prevalence rate, 19%). The Meridian EIA was positive for 71 of the 76 samples, yielding a sensitivity of 93%. The TechLab EIA detected 75 of the 76 positive samples, yielding a sensitivity of 99%. The Meridian and TechLab EIAs had specificities of 100 and 93%, respectively. These data indicate that both EIAs are suitable alternatives to the cytotoxin assay in routine diagnostic laboratories. However, confirmation of TechLab EIA-positive test results by the cytotoxin assay remains necessary.     

Detection of Giardia lamblia and Cryptosporidium parvum antigens in human fecal specimens using the ColorPAC combination rapid solid-phase qualitative immunochromatographic assay

The ColorPAC Giardia/Cryptosporidium (Becton Dickinson) is a solid-phase qualitative immunochromatographic assay that detects and distinguishes between Giardia lamblia and Cryptosporidium parvum in human stool. Agreement between the Alexon-Trend ProSpecT Giardia Rapid EIA and the ColorPAC assay was 166 of 172 (96.5%). Agreement between the Alexon-Trend ProSpecT Cryptosporidium Rapid EIA and the ColorPAC assay was 169 of 171 (98.8%). No cross-reactions were seen with other parasites or human cells.     

Evaluation of Four Enzyme Immunoassays for the Detection of Giardia lamblia Antigen in Stool Specimens

 Four enzyme immunoassays for the detection of Giardia lamblia antigen in stool specimens were evaluated: the ProSpecT Giardia Microplate Assay (Alexon, USA), the Giardia CELISA (Cellabs, Australia), the DSl-Giardia-ELISA (DSL, Germany), and the Melotest Giardiasis Ag (Melotec, Spain). Microscopic examination and enzyme immunoassays were performed on 168 stool specimens collected from 168 patients suspected to have giardiasis. All assays were easy to perform. The ProSpecT Giardia assay had the highest sensitivity of the assays evaluated (91%), and its interpretation was the easiest. The sensitivity of the three other assays ranged from 63 to 81%. The ProSpecT Giardia assay can be useful to detect Giardia lamblia and may replace microscopic examination in areas of high endemicity.     

Commercial assay for detection of Giardia lamblia and Cryptosporidium parvum antigens in human fecal specimens by rapid solid-phase qualitative immunochromatography

The ImmunoCard STAT! Cryptosporidium/Giardia rapid assay (Meridian Bioscience, Inc.) is a solid-phase qualitative immunochromatographic assay that detects and distinguishes between Giardia lamblia and Cryptosporidium parvum in aqueous extracts of human fecal specimens (fresh, frozen, unfixed, or fixed in 5 or 10% formalin or sodium acetate-acetic acid-formalin). By using specific antibodies, antigens specific for these organisms are isolated and immobilized on a substrate. After the addition of appropriate reagents, a positive test is detected visually by the presence of a gray-black color bar (regardless of the intensity) next to the organism name printed on the test device. A control is included in the device. Steps include tube preparation (buffer, patient specimen, conjugates A and B), testing (addition of sample onto the test device), and visual reading (total time, 12 min). Test performance was evaluated with known positive and negative stool specimens (170 specimens positive for Giardia and 231 specimens negative for Giardia) (85 specimens positive for Cryptosporidium and 316 specimens negative for Cryptosporidium); they were tested with trichrome, iron-hematoxylin, or modified acid-fast stains or the Meridian Bioscience, Inc., Giardia/Cryptosporidium Merifluor combination reagent; specimens with discrepant results were retested by using the Merifluor combination reagent. On the basis of the results of the reference methods, the sensitivities, specificities, and positive and negative predictive values were as follows: for G. lamblia, 93.5, 100, 100, and 95.5%, respectively; for C. parvum, 98.8, 100, 100, and 99.7%, respectively. False-negative results for G. lamblia were obtained with specimens with low parasite numbers (n = 7) or specimens containing trophozoites only (n = 3); one specimen with a false-negative result contained numerous cysts. The one specimen false negative for C. parvum was confirmed to be positive by immunofluorescence. No cross-reactivity was seen with 10 different protozoa (152 challenges), nine different helminths (35 challenges), or human cells (4 challenges) found in fecal specimens. This rapid test system may be very beneficial in the absence of trained microscopists; however, for patients who remain symptomatic after a negative result, the ova and parasite examination and special stains for other coccidia and the microsporidia should always remain options.     

Comparison of four commercially available rapid enzyme immunoassays with cytotoxin assay for detection of Clostridium difficile toxin(s) from stool specimens.

Rapid (2.5- to 3.5-h) enzyme immunoassays (EIAs) for the detection of Clostridium difficile toxins have been developed. We report the results of simultaneous testing of 700 fresh stool specimens by the tissue culture cytotoxin assay and four EIAs (Bartels Prima System C. difficile Toxin A EIA, Cambridge Biotech Cytoclone A+B EIA, Meridian Diagnostics Premier C. difficile Toxin A EIA, and TechLab C. difficile Tox-A Test EIA). In cases of disagreement, culturing for toxigenic C. difficile was performed. A total of 61 (8.7%) specimens from 46 patients were positive for C. difficile toxin. The sensitivity of the cytotoxin assay was 87%, and that of culture was 93%. In comparison with the cytotoxin assay results, the sensitivity and specificity of the EIAs were as follows: Bartels, 87 and 96%; Cambridge, 89 and 99%; Meridian, 87 and 98%; and TechLab, 87 and 95%, respectively. In comparison with the cytotoxin assay plus toxigenic culture results, the sensitivity and specificity of the EIAs were as follows: Bartels, 84 and 97%; Cambridge, 85 and 99%; Meridian, 79 and 98%; and TechLab, 80 and 96%, respectively. The EIAs varied in positive predictive values (PPVs). A high PPV was seen with the Cambridge EIA (96%); lower PPVs were seen with the TechLab (64%), Bartels (72%), and Meridian (80%) EIAs because of high false-positive rates. The negative predictive values (98 to 99%) were excellent with all EIAs. Results were indeterminant with 0.3% of the samples by the Meridian EIA and 3% by all the other EIAs. Although the EIAs were less sensitive than the cytotoxin assay, they provide same-day results and may be useful in laboratories without tissue culture facilities.     

Evaluation of an enzyme-linked immunosorbent assay for detection of Cryptosporidium spp. in stool specimens.

We evaluated a commercially produced enzyme-linked immunosorbent assay (ELISA; LMD Laboratories, Inc.) for the detection of Cryptosporidium spp. in 296 stool specimens submitted to the Mayo Clinic parasitology laboratory for routine examination. The specimens examined were fresh (4 specimens), were stored frozen at -65 degrees C (49 specimens), or were preserved in 10% formalin (243 specimens). Results were compared with those obtained by indirect immunofluorescent antibody detection (Merifluor Cryptosporidium/Giardia; Meridian Diagnostics, Inc.). One hundred of the specimens were positive by indirect immunofluorescent antibody and ELISA, while 187 were negative by both methods; 91 of these negative stool samples contained 121 parasites of 17 different species. Eight ELISA false negatives and one false positive were observed. The ELISA sensitivity was 93%, specificity was 99%, and the positive predictive value was 99%. Storage of specimens preserved in 10% formalin or frozen fresh at -65 degrees C for up to 18 months did not appear to affect the results. There was no cross-reactivity with Giardia lamblia (54 negative specimens) or with the 16 other parasites present in the ELISA-negative stool samples. The ELISA is a fast, easy-to-read, and accurate method for the detection of Cryptosporidium spp. in stool specimens.     

Use of an enzyme immunoassay does not eliminate the need to analyze multiple stool specimens for sensitive detection of Giardia lamblia

The relative sensitivities of a commercially available enzyme immunoassay (EIA) (ProSpecT Giardia; Alexon-Trend Inc., Ramsey, Minn.) and conventional ovum-and-parasite (O&P) examination for the detection of Giardia lamblia in preserved stool specimens were determined. Paired stool samples collected independently within a 7-day period from 103 patients were analyzed by both methods. A total of 54 specimens from 30 patients (18 asymptomatically infected with G. lamblia and 12 with symptoms consistent with intestinal giardiasis) were determined to be positive for G. lamblia, of which 48 (88.9%) were positive by microscopy and 52 (96.3%) were positive by EIA. Both specimens submitted were positive for G. lamblia by O&P examination for 66.7% (20 of 30) of the positive patients; for 26.7% (8 of 30) a single specimen was positive by O&P examination, and for 6.7% (2 of 30) of those determined to be infected with G. lamblia, both samples were negative by microscopy. The sensitivity of conventional O&P examination was somewhat higher in symptomatically infected individuals, with 75% (9 of 12) of patients in this category having G. lamblia detected in both samples, compared with 61% (11 of 18) of asymptomatic patients. A total of 24 positive patients (80%) had G. lamblia antigen detected by EIA in both submitted samples, 4 positive patients (13.3%) had one specimen positive by EIA, and the EIA was negative in both specimens from 2 infected individuals (6.5%), the sensitivity of EIA was substantially equivalent in asymptomatic and symptomatic individuals (77 versus 83% of patients with positive results on both specimens). Although the sensitivity of EIA for the detection of G. lamblia on a single stool specimen was somewhat higher than that of conventional O&P examination in symptomatic patients (83 versus 75%), in asymptomatic patients (77 versus 61%), and overall (80 versus 67%), examination of two specimens by either EIA or microscopy was necessary to achieve a diagnostic sensitivity of greater than 90%.     

Evaluation of the ProSpecT Microplate Assay for detection of Campylobacter: a routine laboratory perspective

Objectives  To evaluate the use of the new enzyme-linked immunosorbent assay, the ProSpecT Campylobacter Microplate Assay (Alexon-Trend, Minneapolis, MN, USA), which allows 2-h detection of both Campylobacter jejuni and Campylobacter coli antigen directly in stool specimens.
Methods  Over 4 months, all stool samples preserved in Cary–Blair medium, or fresh specimens, from non-hospitalized children and HIV-infected patients (adults and children), submitted to our laboratory were evaluated with the ProSpecT Campylobacter Microplate Assay. Results were compared with those obtained by routine culture methods using both a specific medium and a filtration method for the recovery of Campylobacter spp.
Results  Of the 1205 stool specimens cultured, 101 were found to be positive for either C. jejuni or C. coli , giving an overall recovery rate of 8.38%. Ninety samples were positive by both culture and ProSpecT Campylobacter Microplate Assay, and 11 were positive by culture only, giving a sensitivity of 89.1%. In addition, of 1104 samples negative by culture, 25 were initially positive by ProSpecT Campylobacter Microplate Assay. We found no cross-reaction with other bacterial enteropathogens isolated from stool specimens. These results thus confirm a high specificity (97.7%) for both C. jejuni and C. coli. The positive and negative predictive values found were 78.3% and 99%, respectively. There was no statistically significant difference in sensitivity and specificity if the stool was fresh or preserved with Cary–Blair medium.
Conclusion  These data suggest that the ProSpecT Campylobacter Microplate Assay is a rapid and easy-to-use test for the detection of both C. jejuni and C. coli in stool specimens. It could be used for patients for whom early antibiotic therapy is needed or for epidemiologic studies.     

Evaluation of three commercial enzyme immunoassay kits for detecting faecal Clostridium difficile toxins.

The detection of faecal cytotoxicity using tissue culture was compared with three commercial Clostridium difficile enzyme immunoassay (EIA) kits; Premier C difficile toxin A (Meridian Diagnostic, Inc.); CD-TOX C difficile toxin A (Porton Cambridge); and Cytoclone A+B EIA (Cambridge Biotech Corporation). Of 160 faecal samples examined by all four methods, 52 (32.5%) were cytotoxic, 44 (27.5%) were positive by Premier, 48 (30%) by CD-TOX EIA, and 50 (31.3%) with Cytoclone. When compared with detection of cytotoxicity by tissue culture assay, the following performance indices were obtained: Premier, sensitivity 84.1%, specificity 99.1%, positive predictive value (PPV) 97.8%, negative predictive value (NPV) 93%; CD-TOX, sensitivity 92.3%, specificity 88.0%, PPV 78.7%, NPV 95.9%; Cytoclone, sensitivity 96.2%, specificity 93.5%, PPV 87.7%, NPV 98.1%. EIA results were available within three hours, whereas the results of the cytotoxin assay were available after 24-48 hours. All three kits provided satisfactory results and, although relatively expensive, all could be used in the laboratory effectively to screen for diarrhoeal disease associated with C difficile.     

Stool diagnosis of giardiasis using a commercially available enzyme immunoassay to detect Giardia-specific antigen 65 (GSA 65).

A commercially available enzyme immunoassay for the diagnosis of giardiasis was evaluated in a clinical trial. The ProSpecT/Giardia diagnostic test (Alexon, Inc., Mountain View, Calif.) was compared with the standard ova and parasite (O&P) microscopic examination. Additionally, several widely used stool fixatives and a commonly used transport medium were assessed for compatibility with the immunoassay. A total of 325 stool specimens were collected and used to evaluate assay performance. Of those, 93 specimens were collected from symptomatic Giardia O&P-positive patients and 232 specimens were randomly collected from patients as part of a routine health screening procedure. All 93 Giardia O&P-positive stool specimens were strongly positive by visual and spectrophotometric examination using the immunoassay. Of the 232 randomly collected specimens, 16 were positive by O&P examination and immunoassay, 6 were negative by O&P examination but positive by immunoassay, and 1 was positive by O&P examination and negative by immunoassay. There was substantial supportive evidence that indicated that the six immunoassay-positive, O&P-negative specimens were true-positives. When these six specimens were accepted as true-positives, the immunoassay detected almost 30% more cases of Giardia infection than did O&P examination. Its sensitivity and specificity were 96 and 100%, respectively, while the sensitivity and specificity of O&P examination were 74 and 100%, respectively. The immunoassay also performed well on specimens treated with 10% neutral Formalin, sodium acetate-Formalin fixative, and Cary-Blair transport medium. However, the test was not compatible with polyvinyl alcohol-treated specimens. Overall, the ProSpecT/Giardia test was a sensitive, specific immunoassay which was easy to run and interpret. It offers a simple solution to traditional difficulties encountered in diagnosing Giardia infection.     

Comparison of Nine Commercially Available Enzyme-Linked Immunosorbent Assays for Detection of Giardia lamblia in Fecal Specimens

Overall performance, including ease of use, total hands-on time, incubation and processing times, sensitivity, and specificity, of each of nine enzyme-linked immunosorbent assays (ELISAs) were compared by using 222 individual fecal samples submitted for the detection of Giardia lamblia. The assays evaluated were manufactured by Alexon, Inc., Cambridge Biotech Corp., Meridian, Inc., and Trend Scientific, Inc. All assays used polyclonal antibodies except the “new and improved” Microplate (direct and diluted methods) by Alexon, which is a monoclonal antibody assay. Seventy specimens were positive for G. lamblia by ELISA, ova and parasite test, and/or direct fluorescent-antibody assay. One hundred fifty two were negative by all three methods. Sensitivities and specificities ranged from 88.6 to 100% and 99.3 to 100%, respectively. The total hands-on time needed to run one specimen ranged from 1 min to 2 min 17 s per specimen. All except one commercially available ELISA were found to be rapid, sensitive, and specific for the detection of G. lamblia in fecal specimens.     

Cryptosporidiosis: comparison of three diagnostic methods and effects of storage temperature on detectability of cryptosporidia in cattle faeces

Three diagnostic methods (a modified Ziehl-Neelsen staining technique (MZN), a negative staining with carbol fuchsine (CF) and a commercial enzyme immunoassay (EIA) kit, ProSpecT? Cryptosporidium Microplate Assay (Remel, Lenexa, KS, USA)) for detection of Cryptosporidium oocysts in cattle faeces were compared regarding sensitivity and suitability under routine laboratory conditions, with particular emphasis on sample storage. In the 103 faecal samples examined, cryptosporidia infections were detected significantly more often by EIA (p<0.05; n=76) than by MZN (n=65) if ten random fields were evaluated microscopically, but not if the whole coverslip was scanned. In contrast, sensitivities of EIA and CF (n=69) did not differ significantly. Results were obtained very rapidly by CF. However, the hands-on time of CF is comparable to EIA, while MZN is more time consuming. EIA is more expensive than CF and MZN but easy to perform and to evaluate and does not need considerably experienced staff in contrast to CF and MZN. Moreover, 45 faecal samples stored for up to 27 days at different temperatures (+6°C, +16°C, +30°C, +40°C) were examined. The sensitivity of microscopic detection of oocysts in stained smears (CF, MZN) decreased in a temperature and time-dependent manner, while EIA results were not influenced by sample storage at any temperature.     

Evaluation of new rapid commercial enzyme immunoassay for detection of Cryptosporidium oocysts in untreated stool specimens.

Sixty-six stool specimens were evaluated by the ProSpecTR Cryptosporidium rapid enzyme immunoassay (EIA) (Alexon, Sunnyvale, Calif.). Approximately 2 g of untreated stool suspended in buffer was filtered through membranes labelled with anti-Cryptosporidium-specific antigen antibody. Anti-Cryptosporidium-specific antigen antibody was labelled with biotin, horseradish peroxidase conjugated to streptavidin, and tetramethylbenzidine, and each labelled antibody was added in sequence to the membranes. Each membrane had a positive control and test area. EIA results were compared with those of the modified acid-fast procedure. Twenty-three specimens were positive by the initial acid-fast procedure and the EIA. Forty-two specimens were negative by the initial acid-fast test and the EIA. One specimen was negative by the initial acid-fast test and positive by the EIA (sensitivity, 100%; specificity, 98.5%). This technique is easy to use by comparison with the cumbersome, labor-intensive, and more subjective microscopic methods currently available, and its sensitivity equals that of current microscopic methods.     

Evaluation of ColorPAC Giardia/Cryptosporidium Rapid Assay and ProSpecT Giardia/Cryptosporidium Microplate Assay for Detection of Giardia and Cryptosporidium in Fecal Specimens

Detection of Giardia and Cryptosporidium in clinical stool specimens using the ColorPAC and ProSpecT enzyme immunoassays revealed 98.7% agreement for Giardia detection and 98.1% agreement for Cryptosporidium detection. Sensitivities were uniformly 100%. The specificities of the ColorPAC immunoassay for Giardia and Cryptosporidium detection were 100 and 99.5%, respectively, and those for the ProSpecT assay were 98.4 and 98.6%, respectively. The false-positive reactions with the ProSpecT assay occurred with specimens that were grossly bloody.     

Detection of Giardia lamblia and Entamoeba histolytica in Stool Samples by Two Enzyme Immunoassays

 Two commercially produced enzyme immunoassays (EIAs) to detect antigens of Giardia lamblia and Entamoeba histolytica in stool specimens were evaluated. A total of 276 stool specimens were collected from patients who presented with various medical complaints in the outpatient clinic of the Department of Infectious Diseases and Tropical Medicine, University of Munich. Every specimen was examined by conventional microscopy and tested by both EIA kits. When microscopy was used as the reference standard, the EIA kit detecting Giardia lamblia showed a sensitivity of 100% and a specificity of 99.6%. The EIA kit detecting Entamoeba histolytica had a sensitivity of 81.8% and a specificity of 99.2%. Both tests showed no cross-reactivity with other intestinal protozoa. Antigen detection by EIA has the potential to become a valuable tool capable of making stool diagnostics more effective, although it should not be considered as a replacement for microscopic examination, since other potential pathogens could otherwise escape detection.