Practice Guidelines for Ordering Stool Ova and Parasite Testing in a Pediatric Population

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1 CLINICAL MICROBIOLOGY AND INFECTIOUS DISEASE Original Article Practice Guidelines for Ordering Stool Ova and Parasite Testing in a Pediatric Population AMIN KABANI, MD, FRCPC, GISELE CADRAIN, RT, CYNTHIA TREVENEN, MD, FRCPC, TAJ JADAVJI, MD, FRCPC, ' AND DEIRDRE L. CHURCH, MD, PHD, FRCPC " A comprehensive utilization review was done of all stool ova and parasite examinations performed at a pediatric hospital during a -year period from June,989 to July,99. A total of,6 stool specimens were surveyed from, children. Forty-one percent (,08) of the workload was from inpatients, 7% (976) was from emergency room (ER) visits/other outpatients, and % () was from patients attending the gastroenterology (GI) clinic. The prevalence of enteric parasites in hospitalized children was % ( of 89) compared to rates of 0% (7 of 70) and % (0 of ) for children attending the ER/other outpatient clinics and GI clinic, respectively. Giardia lamblia was found most often (%( of 6]), followed by Dientamoeba fragills (% of 6), Entamoeba coli (6% ( of 6]), Blastocysts Aomin the past, it has been recommended that up to three separate, sequentially collected stool specimens should be examined in the laboratory to accurately diagnose enteric parasitic infection. This practice was widely adopted after studies showed that the rate of recovery of Entamoeba histolytica from asymptomatic patients increased from 0% with only one stool sample to 90% after examination of six stool samples. Several other studies have also reported that multiple specimens are required to achieve adequate sensitivity of recovery of parasites. However, these studies were epidemiologic in nature, aimed at primarily diagnosing asymptomatic E histolytica excretion, and stool concentration methods were not always used. It has become clear more recently that these data may not be entirely applicable for the di- From the 'Departments of Microbiology and Infectious Diseases, Medicine, and Pediatrics, University of Calgary, Calgary, Canada; and the* Clinical Laboratory (Microbiology), Alberta Children's Hospital. Alberta, Canada. Manuscript received February, 99; revision accepted April 9, 99. Address reprint requests to Dr. Church: Director of Microbiology, Alberta Children's Hospital, 80 Richmond Rd., SW, Calgary, Alberta, Canada TT-C7. Ms (% [9 of 6), Cryptosporidium (8% [ of 6), EndoUmax nana (% [6 of 6)), Enterobius vermicularis (% [ of 6]), Hymenolepis nana (% [ of 6]), and Iodamoeba buetschlii ( % [ of 6]). Most children were colonized/infected with a single parasite (8%) with a much smaller number having two or more parasites. Only nine children (6%) who were immunocompetent and hospitalized for more than days were found to have enteric parasites. Over the past 8 months, significant sustainable cost savings have resulted from the implementation of practice guidelines for ordering pediatric stool ova and parasite examinations (Key words: Stool ova and parasite examinations; Pediatrics; Practice guidelines) Am J Clin Pathol 99; 0:7-78. agnosis of enteric parasitic infections in acutely symptomatic patients with watery diarrhea. 6 " 0 In particular, the sensitivity of examining a single versus multiple stool specimens for enteric parasites, as well as the clinical relevance of doing stool parasite tests in hospitalized patients has been examined. 90 Both of these recent studies in predominantly adult hospitalized populations, demonstrated no adverse clinical effects of instituting a policy of only doing a single initial stool ova and parasite exam, and rejecting specimens that had been requested on patients hospitalized for more than days. 9-0 However, because young children generally have a much higher incidence of certain types of symptomatic enteric parasitic infection than older children and adults,"" it was important to do a comprehensive utilization review of stool ova and parasite testing in a pediatric population before implementing practice guidelines that were developed from predominantly adult data. In particular, it was important to determine the yield from a single versus multiple stool ova and parasite tests in children, while establishing a clinically safe cutoff point in days for refusing stool parasite specimens in hospitalized children. Downloaded from by guest on March 0, 06 7

2 KABANI ET AL. 7 Guidelines for Stool 0 c P Testing in Pediatrics Practice guidelines that developed at our hospital after this study are outlined along with an assessment of the impact and sustainability of implementation of these guidelines. Patient Population MATERIALS AND METHODS The Alberta Children's Hospital is a tertiary regional referral hospital in Calgary, which is also affiliated with the Faculty of Medicine, University of Calgary. As such, the hospital serves a population base of. million people, seeing children referred from southern Alberta, southwestern British Columbia, northern Montana, and southeastern Saskatchewan. During the time of this study, approximately 6,700 children per year were hospitalized, 6,000 children per year attended the emergency room, and another 60,000 children per year were seen as outpatients in the various Diagnostic and Therapeutic Clinics (DAT) and physicians' offices. Laboratory Methods All stool specimens were collected and transported in sodium acetyl acetate formalin (SAF). Preserved stools were then concentrated using a standard formalin-ethyl acetate method. 6 Two slides were preparedone slide, made from the washed stool, was stained permanently using a modified iron hematoxylin/kinyoun stain, 7 and another slide from the stool concentrate was examined unstained. The stained preparation was examined by a technologist for minutes under 0X, 0X, and 00X magnification, and the direct smear was examined using a mm X 0 mm coverslip for 0 minutes using the same magnification. Data Collection and Analysis Statistical stool ova and parasite examination utilization data were initially compiled from the Microbiology laboratory's logbook for years from June, 989 through July, 99. Information about the total number of specimens, date received, number of specimens per patient, ordering location, date of hospitalization, and the number and identification of the positive specimens was recorded. Detailed chart reviews were then done on all children with parasites to determine the clinical symptoms, the length of stay if admitted, and the relationship of positive stool parasite tests to their number of days in hospital. All stool ova and parasite samples were then classified as inpatient versus outpatient, with inpatient specimens being further identified as to the length of time the child had been admitted before collection of stool specimens. Detailed analyses of all stool specimens coming from specific ordering locations (eg, emergency room/other outpatient clinics, gastroenterology, and oncology clinics) were also done. Practice guidelines were then developed based on the results of this study. After the above criteria had been established, the workload reduction in the microbiology laboratory was measured over the subsequent year and projected cost savings were calculated. RESULTS Epidemiology of Enteric Parasitic Infections For the -year study period from June, 989 to July, 99, a total of,6 stool ova and parasite tests were surveyed from, children. Forty-one percent (,08) of the specimens were received from inpatients, 7% (976) were from the emergency room/other outpatient clinics, and % () were from the Gastroenterology clinic. No increase in enteric parasitic infection was found during any particular time of the year for any type of infection (Fig. ). Giardia lamblia ( of 6, %) and Dientamoeba fragilis of 6, %) infections accounted for the majority of positive stool ova and parasite examinations, with Entamoeba coli ( of 6, 6%), Blastocystis hominis (9 of 6, %), Cryptosporidium spp.( of 6, 8%), Endolimax nana (6 of 6,%), Hymenolepsis nana ( of 6,%), Enterobius vermicularis ( of 6, %) and lodamoeba buetschlii ( of 6, %) being found much less frequently. No differences were seen in the types and incidence of enteric protozoal colonization or infection between children admitted to the hospital versus those attending the emergency room or other outpatient areas (data not shown). Most of the children (8%) were infected/colonized by a single parasite, but % had two parasites, and % had three or more parasites isolated. Ordering Practices for Hospitalized Children A total of,08 stool parasite examinations were done from 89 hospitalized children during the study (Table ). Most patients had a single stool ova and parasite examination ordered, but of,08 (8%) of the stool specimens represented multiple test requests ( or more samples) from some children. There were hospitalized children with enteric parasites, and most of the time (86%), the organism(s) were identified in every stool sample submitted for examina- Downloaded from by guest on March 0, 06 Vol. ' No.

3 7 CLINICAL MICROBIOLOGY AND INFECTIOUS DISEASE Original Article ENTERIC PARASITES OE. vermicularis HH. EI. butschleli E. nana ECr yptosporidium SB. HE. coli QD G nana Hominis f ragilis lamblia FIG.. Frequency of different types of enteric parasitic infections by month (June 989-July 99). No. of Stool Specimens per Child > Total tion. In fact, of children (9%) had positive stool examinations after the first specimen, and the second stool specimen was diagnostic in the remaining three (8%) children. The three children who were not diagnosed on the initial stool samples included two cases of and another child with Giardiasis. Eight children (7%) ( [8.%] children were detected on day, and another [8.%] children were detected TABLE. NUMBER OF STOOL OVA AND PARASITE SPECIMENS RECEIVED VERSUS POSITIVITY FOR ENTERIC PARASITES FROM HOSPITALIZED CHILDREN No. of Children Total No. ( /o) of Stool Specimens 666(6) 9(8) 9(),08 6(6) No. ( /o) of Children With Positive Enteric Parasites 0(7) 6(7) 7(0) (6) Parasites* Enana + E nana H nana + E vermicularis No. of Positive Specimens-^ 6 Downloaded from by guest on March 0, 06 * Eight of (%) children had multiple enteric parasites found. t Three of (8.%) children who had multiple stool specimens examined only had parasites in a single sample. A.J.C.P.- September 99

4 KABANI ET AL. 7 Guidelines for Stool O and P Testing in Pediatrics TABLE. TIMING OF POSITIVE STOOL OVA AND PARASITE RESULTS FROM HOSPITALIZED CHILDREN* Days of Hospitalization Enteric Parasites > Total Giardia lamblia Dientamoebafragilis Entamoeba coli Blastocytis hominis Endolimax nana Hymenolepsis nana Total (%) 7(6) (8) 9(9) (8.) (8.) 7f For all children, the timing of only the initial positive culture is recorded. t Eight of children were colonized/infected with more than one parasite. after day ) with enteric parasites would have been "missed" if stools collected after days of hospitalization were not processed as per the currently recommended policy for hospitalized adults 90 (Table ). All of these children had pathogenic infections including, four (0%) with, two (%) with, and two (%) with Cryptosporidium spp. infection. Ordering Practices for Outpatients A total of,7 stool parasite examinations were done from 70 children attending the emergency room/other outpatient areas or the gastroenterology clinic. Most ambulatory children had or more stool specimens (,06 of,7 [68%]) submitted for parasite examination (Table, A and B). Ambulatory children had much higher rates of enteric parasitic infection overall than hospitalized children; 7 of 70 (0%) of children from the emergency room/other outpatient areas, and 0 of (%) of children from the gastroenterology clinic had one or more protozoa. infection was commonly found either alone or along with other enteric parasites, especially among children referred to the gastroenterology clinic for investigation of chronic diarrhea. Overall, there were 77 ambulatory children identified with enteric parasites. Most of these infections were diagnosed by a single stool specimens; 70 of 77 (9%) were found to have one or more parasites on the initial sample submitted to the laboratory, whereas only 7 of 77 (9%) required an additional stool sample to be diagnosed (Table, A and B). Two children of 7 (%) attending the emergency room, who were found to have would have been missed if only one stool specimen had been examined. In both cases, Giardiasis was found on the second of three stool samples. However, the clinical significance of these two infections could not be assessed because of the retrospective nature of this study. A greater number of children attending the gastroenterology clinic would have been missed if more than one stool had not been examined including: of 0 (7%) children were found to have,, or infections on examination of subsequent stool specimens when the first or second proved negative. In all cases, these parasitic infections were considered clinically significant. Impact of Implementation Practice Guidelines of Stool Ova and Parasite Based on these study results, the following two guidelines were implemented during 99:. Only a single stool ova and parasite examination is ordered initially on children with acute diarrhea regardless of location (eg, ambulatory or recently hospitalized children [during the first days of their stay]).. Stool ova and parasite tests are discouraged on hospitalized children who develop diarrhea after their fourth hospital day. Medical staff were informed of these laboratory policy changes when the results of the utilization review were presented at Pediatric Grand Rounds and through the circulation of a hospital-wide microbiology newsletter. During the first year after the implementation of these guidelines, the laboratory workload from stool ova and parasite testing decreased 7% (approximately 7 specimens per year) overall compared to the previous years studied. This effect has been sustained in the subsequent 99 year. These guidelines have also decreased the overall costs (labor and supplies) for stool ova and parasite examinations by about 0% (approximately $,000 per year). Downloaded from by guest on March 0, 06 Vol. 0.No.

5 76 CLINICAL MICROBIOLOGY AND INFECTIOUS DISEASE Original Article TABLE. NUMBER OF STOOL OVA AND PARASITE SPECIMENS RECEIVED VERSUS POSITIVITY FOR ENTERIC PARASITES FROM OUTPATIENTS No. of Stool Specimens Total No. ( /o) of per Child No. of Children Stool Specimens No. (%) of Children With Positive Enteric Parasites Parasites No. of Positive Specimens i Emergency room/other outpatients* 68 68(7) () 8 6(6) > 8 8() Total Gastroenterology clinicf 9 9(7) 9 78() 8 (7) > 7 (6) 9 (6) (6) (0) () 7 6(0) () 9(6) () E nana E vermiciilaris + H nana H nana E vermiciilaris Ecoli + E nana E nana + I buelschlii + 9 Downloaded from by guest on March 0, 06 Total 9 0 * Four of 7 (8.%) children were colonized/infected with more than one parasite; two of 7 (%) children who had multiple stool specimens examined only had parasites in a single sample. t Seven of 0 (%) children were colonized/infected with more than one parasite; five of 0 (! 7%) children who had multiple stool specimens examined only had parasites in a single sample. DISCUSSION This study has helped to educate physicians at our institution to consider important clinical and epidemiologic data before indiscriminately ordering stool ova and parasite tests on children presenting with acute watery diarrhea. Enteric parasitic infection with either protozoa and/or helminths is much more likely if the child has a history of recent travel to a Third World country. A.J.C.P. -September 99

6 KABANI ET AL. 77 Guidelines for Stool 0 c P Testing in Pediatrics There is a substantial body of data that currently warrants adoption of a single initial stool ova and parasite examination for the majority of adults suspected of having pathogenic enteric protozoal infections including G lamblia, D fragilis, (when found alone in heavy numbers [>/HPF) in a symptomatic patient), and Cryptosporidium spp. 6 " 0 Although there are limited data regarding the sensitivity of a single stool specimen for the accurate diagnosis of helminth infections, a recent study suggests that worm infections are more easily found than either Giardiasis or Amoebiasis. 8 This observation makes sense because worm eggs are, in general, much larger structures, and thus more easily found on microscopic examination of stool than enteric protozoa. However, when E histolytica infection is suspected, multiple stool samples (up to six sequentially collected specimens) may have to be examined because a single sample has a low yield. 8 Our pediatric study confirms and enhances the findings of previous predominantly adult studies. 90 The vast majority (9%) of the parasites were detected in the first stool specimen, regardless of the type of enteric protozoa found or the child's location (ie, hospitalized versus outpatients). This study also extends the findings of Morris and colleagues, 0 that stool examinations for parasites after days of hospitalization, regardless of the age of the patient or their immune status has a very low diagnostic yield. Only of (8.%) of hospitalized children had positive stool parasite examinations after the fourth day in the hospital, and no children after the first week in the hospital. However, a cut-off of days after admission previously recommended for maximal yield of stool parasite examinations in adults 90 may not be safe for laboratories servicing younger children. Similar to our previous findings for stool culture results, 9 smaller children and neonates who are admitted with acute diarrhea and immediately placed on bowel rest and intravenous fluids, stop stooling. Therefore, the fourth and even thefifthhospital day in this study were found to be crucial in capturing over 90% to 9% of all important enteric parasitic infections in our hospital during the study period. A more flexible cut-off limit of days is recommended for laboratories handling pediatric samples. A single stool ova and parasite examination is initially ordered on all children attending our hospital. In addition, if a stool sample has been submitted to the laboratory from the emergency room, before the child's admission, no additional samples are collected on admission to the ward. The laboratory does not reject duplicate or triplicate stools that have been submitted at the same time as the initial sample. Rather, all of the stool is pooled by the laboratory, and then processed as a single sample for examination. 0- Multiple, sequential stool samples may be warranted for children who have a history of recent travel to a Third World country, due to the increased likelihood of histolytica infection. Because these pediatric guidelines have been implemented, the laboratory has experienced a substantial and sustained decrease in workload and cost that were previously associated with unnecessary stool parasite testing. Universal implementation of similar guidelines among laboratories handling pediatric stool samples would likely have a similar financial impact, while not adversely effecting clinical outcome. Finally, this study demonstrates that practice guidelines devised from previous adult population based studies cannot necessarily be implemented safely in a pediatric population before careful evaluation of their implications for children. REFERENCES. Melvin CM, Brooke MM. Laboratory procedures for the diagnosis of intestinal parasites, rd ed. US Department of Health, Education and Welfare publication no. (CDC) Center for Disease Control, Atlanta, 98.. Procedures for the Recovery and Identification of Parasites from the Intestinal Tract. Proposed Guideline. NCCLS Document M8-P, 99; :6.. Sawitz WG, Faust EC. The probability of detecting intestinal protozoa by successive stool examinations. Am J Trop Med 9;:-6.. Alinca AD, Fadell AJ. Advantage of purgation in recovery of intestinal parasites or their eggs. Am J Clin Pathol 99;:9.. Andrews J. The diagnosis of intestinal protozoa from purged and normally passed stools. JParasitol 9;0:-. 6. Senay H, MacPherson D. 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7 78 CLINICAL MICROBIOLOGY AND INFECTIOUS DISEASE Original Article 6. Young K.H, Bullock SL, Melvin DM, Sprull CL. Ethyl acetate as a substitute for diethyl ether in the formalin-ether sedimentation technique. J Clin Microbiol 970; 0: Palmar J. Modified iron hematoxylin/kinyoun stain (Letter). Clin Microbiol News 99; : Marti H, Koella JC. Multiple stool examinations for ova and parasites and rate of false-negative results. J Clin Microbiol 99;: Church DL, Cadrain G, Kabani A, et al. Practice guidelines for ordering stool cultures in a pediatric population. Am J Clin Pai/jo/99;0: Peters CS, Hernandez L, Sheffield N, et al.. Cost containment of formalin-preserved stool specimens for ova and parasites from outpatients. J Clin Microbiol 988; 6:8-8.. Wahlquist SP, Williams RM, Bishop H, et al. Use of pooled formalin preserved fecal specimens to detect Giardia lamblia. J Clin Microbiol 99; 9: Aldeen WE, Whisenant J, Hall D, et al. Comparison of pooled formalin-preserved fecal specimens with three individual samples for detection of intestinal parasites. J Clin Microbiol 99;:-. Downloaded from by guest on March 0, 06 A.J.C.P.-September 99