Specific recommendations regarding frequency of laboratory testing by life stage depend on many factors. One consideration regarding testing frequency is that the incidence of many diseases increases as cats age. Although limited incidence studies have been performed to identify the age of onset of hyperthyroidism in cats, the Task Force recommends that veterinarians strongly consider T4 testing in the apparently healthy mature adult cat. More robust incidence data are needed to develop firmer recommendations.

Comorbidities are extremely common in the senior cat and can impact diagnostic, treatment, and management approaches. Additional considerations relating to diagnosis and management of diseases in mature adult and senior cats are described in the AAFP Senior Care Guidelines.¹² Consensus guidelines and toolkits for the diagnosis and treatment of specific medical conditions are available for more detailed information (see “Guidelines and Toolkits” box).

For cats of all ages, timing and frequency of diagnostics may depend on lifestyle, exposure risks, and geographic location. Retroviral testing recommendations are discussed in detail in the 2020 AAFP Feline Retrovirus Testing and Management Guidelines.¹⁸ In addition to routine deworming, fecal examination should be performed regularly at intervals based on patient health and lifestyle factors.

Heartworm infection ismore difficult to diagnose in cats than in dogs because of lower worm burden, single-sex infections, and infrequency of microfilaremia. HARD, which is an asthma-like inflammatory reaction of the pulmonary tissue to immature larval stages, is an added complexity relating to heartworm exposure in cats. Interpretation of antibody and antigen test results is challenging, and a thorough understanding of the limitations of both tests is necessary.More detailed information is available in the American Heartworm Society guidelines.¹²⁵ Testing does not need to be performed before starting preventive treatment.

N-terminal probrain natriuretic peptide has been investigated as a diagnostic tool for cardiac disease in cats.¹³⁸ However, limited information exists about using this test as a screening tool and recommendations cannot be made on the frequency of use for the general population. The decision to use this test should be on an individual basis, and interpretation of test results should be made with an understanding of the sensitivity and specificity of the assay.