The Probability of Specific Diagnoses for Patients Presenting with Common Symptoms to Dutch Family Physicians

,

Original Research

The Probability of Specific Diagnoses for Patients Presenting with Common Symptoms to Dutch Family Physicians

J Fam Pract. 2002 January;51(1):31-36

By

I. M. Okkes, MA, PhD

PDF Download

References

1. Sox HC, Jr. Decision making: a comparison of referral practice and primary care. J Fam Pract 1996;42:155-60.

2. Lamberts H, Hofmans-Okkes IM. Episode of care: a core concept in family practice. J Fam Pract 1996;42:161-67.

3. Kerr LW. Fundamental research at primary care level. Lancet 2000;355:1904-06.

4. Stange KC, Jaén CR, Flocke SA, Miller WL, Crabtree BF, Zyzanski SJ. The value of a family physician. J Fam Pract 1998;46:363-68.

5. Ebell MH, Smith MA, Barry HC, Ives K, Carey M. Does this patient have strep throat? JAMA 2000;284:2912-18.

6. Nutting PA, Green LA. Practice-based research networks: reuniting practice and research around the problems most of the people have most of the time. J Fam Pract 1994;38:335-36.

7. Lamberts H. Episode-oriented epidemiology in family practice: the practical use of the International Classification of Primary Care (ICPC) as illustrated in patients with headache. In: Norton PG, Stewart M, Tudiver F, Bass MJ, Dunn EV, eds. Primary care research: traditional and innovative approaches. Newbury Park, Calif: Sage; 1991;20-72.

8. Donaldson MS, Yordy KD, Lohr KN, Vanselow NA, eds. Primary care: America’s health in a new era. Washington, DC: National Academy Press; 1996.

9. Okkes IM, Oskam SK, Lamberts H. Van Klacht naar Diagnose. Episodegegevens uit de huisartspraktijk. [From complaint to diagnosis: episode data from family practice]. With a CD-ROM. Bussum, the Netherlands: Coutinho; 1998.

10. Hornbrook MC, Hurtado RV, Johnson RE. Health care episodes: definition, measurement and use. Med Care Rev 1985;42:163-218.

11. Solon JA, Feeney JJ, Jones SH, Rigg RD, Sheps CG. Delineating episodes of medical care. Am J Public Health 1967;57:401-08.

12. Okkes IM, Groen A, Oskam SK, Lamberts H. Advantages of a long observation period in episode oriented electronic patient records in family practice. Methods Inf Med 2001;40:229-35

13. Lamberts H, Wood M, eds. ICPC. International classification of primary care. Oxford, England: Oxford University Press; 1987.

14. Lamberts H, Hofmans-Okkes IM. The core of computer based patient records in family practice: episodes of care classified with ICPC. Int J Biomed Comp 1996;42:35-41.

15. Klinkman MS, Green LA. Using ICPC in a computer-based primary care information system. Fam Med 1995;27:449-56.

16. Van Boven C, Dijksterhuis PH, Lamberts H. Defensive testing in Dutch family practice. J Fam Pract 1997;44:468-72.

17. Bentzen N ed. An international glossary for general/family practice. Fam Pract 1995;12:341-69.

18. National Center for Health Statistics. A reason for visit classification for ambulatory care. Hyattsville, Md: National Center for Health Statistics, US Public Health Service; 1979

19. Hofmans-Okkes IM. An international study into concept and validity of the “reason for encounter”. In: Lamberts H, Wood M, Hofmans-Okkes IM, eds. The international classification of primary care in the European community. Oxford, England: Oxford University Press; 1993.

20. Gardner MJ, Altman DG, eds Statistics with confidence. London, England: BMJ; 1989 (floppy disk).

21. Stewart M, Belle Brown J, Weston WW, McWhinney IR, McWilliam CL, Freeman TR. Patient-centered medicine: transforming the clinical method. Thousand Oaks, Calif: Sage; 1995.

22. Green LA, Nutting PA. Family physicians as researchers in their own practices. J Am Board Fam Pract 1994;7:261-63.

23. Franks P, Clancy CM, Nutting PA. Defining primary care: empirical analysis of the National Ambulatory Medical Care Survey. Med Care 1997;35:655-68.

24. National Center for Health Statistics. 1995, 1996, 1997 Ambulatory Medical Care Survey: CD-ROM-series 13. Hyattsville, Md: National Center for Heath Statistics; 1997, 1998, 1999.

25. Okkes IM, Polderman GO, Fryer E, Yamada T, Bujak M, Oskam SK, Green LA, Lamberts H. The role of family practice in different health care systems: a comparison of morbidity data from primary care populations in the Netherlands, Japan, Poland and the US. J Fam Pract 2002;51:72-73.

ABSTRACT

OBJECTIVE: Our goal was to develop reliable data on the probability of specific diagnoses among patients of family physicians (FPs) presenting with common symptoms.

STUDY DESIGN: A group of 54 Dutch FPs recorded the reasons for encounter, diagnoses, and interventions for all episodes of care between 1985 and 1995. Diagnoses could be modified during the episode of care, and a modified diagnosis was applied to all episode data.

POPULATION: We used the listed patient populations of the 54 Dutch FPs, representing 93,297 patient years, 236,027 episodes of care, and 267,897 patient encounters.

OUTCOMES MEASURED: The top 20 diagnoses related to 4 selected presenting symptoms (cough, shortness of breath, general weakness/tiredness, and low back symptom /complaints without radiation), per 100 patients, with 95% confidence intervals, stratified by age. In the standard tables, age-specific cells with fewer than 10 observations were excluded.

RESULTS: The availability of an accurate estimate of prior (pretest) probabilities for common symptoms/complaints has great potential value for family practice as an academic discipline and for family physicians in that it can support their medical decision making. Stratifying data by age groups increases the clinical relevance of the prior probabilities.

CONCLUSIONS: Though collected by Dutch FPs, the data in our study have a high face validity for other clinicians. Still, FPs in other countries should give priority to collecting their own probability databases.

KEY POINTS FOR CLINICIANS

The pretest probability is the likelihood of disease before tests are ordered in a patient with a specific symptom or complaint.
It is very helpful in the diagnosis and management of problems common in family practice.
We have identified the pretest probability for the most common final diagnoses in patients with many common presenting symptom /complaints.

Estimating the probability of disease in unselected patients lies at the heart of the clinical competence of family physicians (FPs).^1,2 This probability is called the prior or pretest probability, because it precedes any diagnostic testing, including the history and physical examination. Based on this knowledge, FPs often decide that since the probability of a serious disease is low, the best thing to do is watchful waiting, thus preventing unnecessary harm and cost to the patient.^3,4 Moderate probabilities may trigger a diagnostic evaluation, and high probabilities may warrant empiric therapy without further diagnostic confirmation. For example, knowing that the probability of gastric carcinoma is exceedingly rare for a dyspeptic patient younger than 40 years supports a diagnostic approach that does not include initial endoscopy. A moderate probability of strep throat is a situation where a rapid strep test may be helpful.⁵ Understanding the high prior probability of a urinary tract infection in young healthy women with dysuria might allow an FP to confidently institute a telephone-based protocol, including empiric treatment for selected patients.

The development of a prior probabilities database requires access to large diverse practice populations with adequate continuity of care and good documentation of all episodes of care.^2,6,7 An “episode of care” is defined as a health problem from the first encounter with a health care provider through the completion of the last encounter related to that particular problem.^2,8.10,11 Early in an episode of care, FPs will often assign a symptom diagnosis such as chest pain, gastric pain, or otalgia; a substantial number of these diagnoses will change over time. Therefore, the observation period should allow for the most important modifications of diagnoses to become visible. Because 1-year incidence and prevalence rates are usually calculated, at least a 1-year study period is required; however, a longer period is preferable, especially for information on chronic diseases.¹²

Episodes of care are based on the relationship between the patient’s reasons for encounter (RFE), the physician’s diagnostic interpretation, and the related interventions over time.¹³ Episodes of care are clearly distinguished from episodes of disease and episodes of illness. An episode of disease begins with its onset and continues until its resolution or the patient’s death, while an episode of illness refers to the period that someone suffers from symptoms or complaints experienced as illness. Not every disease, and certainly not every illness, results in an episode of care.^2,13,14 Most episodes of care, however, are part of an episode of disease and/or illness. Health maintenance episodes can be considered a special form of episodes of care.^10,11 For example, screening for breast cancer (an episode of health maintenance) may prove the existence of the episode of disease well before the patient has symptoms (an episode of illness); an episode of care will follow.

The development of a prior probabilities database also requires a primary care–specific system of classification. The International Classification of Primary Care (ICPC) includes approximately 200 symptoms/complaints and 300 diagnoses common in family practice. Almost all have an incidence of at least 1 per 1000 patients per year.^13,15