A British Longhair needs 2 pieces of paperwork before it needs a vet: a PKD1 DNA result and an F9 clotting result. Both are one-time tests, both are cheapest before the cat is 12 weeks old, and both change what you do for the next 15 years. After that the plan is 2 scans and a blood tube: kidney ultrasound at 10 months and again at 2 years, an echo from 12 months, and a clotting check before any surgery.
1. The 2 DNA tests, run once
Polycystic kidney disease (PKD) in this family is autosomal dominant: one copy of the PKD1 variant is enough, so an affected cat has an affected parent and passes it to about half its kittens. A cheek swab or EDTA blood sample gives a yes or no answer for 40 to 80 dollars, with results in 7 to 21 days. Hemophilia B is X-linked, carried on the factor IX gene: males with the variant bleed, females are usually carriers who pass it on without showing it, which is why a tested queen matters more than a tested tom. A combined panel costs 90 to 160 dollars.
Neither result expires. Retest only if the certificate names a different cat, a different laboratory, or a variant the lab has since reclassified.
2. Kidneys: 10 months, then 2 years
A DNA result tells you risk, not the number of cysts, and that is what the ultrasound is for. Cysts as small as 1 to 2 mm are visible on a good scan but rarely before 6 months, so 10 to 12 months is the first useful look and 24 months the second: a cat clear at 10 months can still develop cysts within a year. Ask for kidney length in mm on the report: 35 to 45 mm is the usual adult range, and a cat with cysts needs creatinine, urine specific gravity and blood pressure every 6 to 12 months rather than every 2 years.
The numbers that move a plan: a urinalysis showing urine specific gravity below 1.035 means concentrating ability is slipping, creatinine above the laboratory's upper limit (commonly around 1.6 to 2.1 mg/dL, ranges vary by analyser) is the trigger for IRIS staging, SDMA above 14 µg/dL flags loss of filtration earlier than creatinine, and systolic blood pressure above 160 mmHg on 2 visits means treatment. Kidney diets and phosphate binders are prescribed by the veterinarian; the owner's job is the water bowl, the weight, and the 6-month recheck.
3. Heart: echo from 12 months, then every 12
Hypertrophic cardiomyopathy (HCM) is the second scan, and the one that cannot be replaced by a swab: the validated MYBPC3 tests sold for cats cover the Maine Coon and Ragdoll variants, not this breed. Ask for 3 values in writing: maximal diastolic wall thickness (under 5.0 mm normal, 5.0 to 5.9 mm a 6-month recheck, 6.0 mm or more the usual definition), LA/Ao (1.5 or below normal, above 1.7 a dilating atrium), and SAM yes or no. Any murmur earns an echo within 4 weeks at grade 1 to 2, within 7 days at grade 3 or with a gallop. Before the echo, a chest radiograph gives the vertebral heart score: above about 9.3 with a large left atrium means the scan is not optional.
4. Blood and lymph nodes: the 2 non-routine watches
Hemophilia B changes surgery, not daily life. Before any dental, neuter or extraction, ask for a platelet count and an APTT: a prolonged APTT with a normal platelet count is the pattern that sends the sample on to a factor IX assay. A severely affected male (factor IX activity under 5%) bleeds from a simple intramuscular injection, so vaccines go subcutaneously, aspirin and NSAIDs are off the list, and plasma or factor replacement is a hospital decision. Mild cases are found by accident on a pre-operative panel, which is exactly why the panel is worth doing once.
Autoimmune lymphoproliferative syndrome (ALPS) is rare and mostly shows up in the first 2 years as lymph nodes that stay enlarged. The working rule is 4 weeks: a node over 20 mm that is still there after 4 weeks, or nodes in 3 or more body regions, or a kitten that stops gaining weight, goes to the vet with a full blood count. Corticosteroids and other immunosuppressants are prescribed by the veterinarian after the diagnosis, never before it, because steroids blur the sample the diagnosis depends on.
5. The screening calendar
| Age | PKD1 swab | Kidney ultrasound per year | Echo per year | Clotting panel |
|---|---|---|---|---|
| 8 to 12 weeks | 1 (once, lifetime) | 0 | 0 | 1 F9 test |
| 10 to 12 months | 0 | 1 | 1 (baseline) | APTT before any surgery |
| 2 years | 0 | 1 (second look) | 1 | 0 |
| 3 to 6 years | 0 | 0, or 1 if cysts found | 1 | 0 |
| 7 years and up | 0 | 1 (with SDMA and BP) | 1 | 0 |
6. Four signals you can see at home
- Water and litter. A cat drinking more than 45 mL/kg a day, or producing clumps that doubled in 2 weeks, is the earliest kidney signal available without a needle.
- Sleeping respiratory rate. 30 seconds, twice a week, 30 per minute as the ceiling; 40 once or 30 three times means a call.
- Bruising and nosebleeds. A 10 mm bruise after a vaccine, blood on a toy, or gums oozing 5 minutes after a nail trim points at clotting.
- Nodes and weight. Feel under the jaw and behind the knee every 2 weeks; a 20 mm node that lasts 4 weeks, or 100 g lost in a month, is a blood count.
7. Hours, not appointments
| What you see | Number | Act within |
|---|---|---|
| Open-mouth breathing at rest | any | 0 to 1 hour |
| Sleeping respiratory rate | 40+ once or 30+ x3 | 2 hours, else 24 hours |
| Bleeding that will not stop | 5 minutes of pressure | 30 minutes |
| No urine for a day | 24 hours | 2 hours |
| Not eating, overweight cat | 24 hours | 4 to 6 hours |
| Vomiting more than 3 times | 3 in 12 hours | 6 hours |
| Node over 20 mm | 4 weeks | 7 days |
| Weight down 5% in 30 days | 5% | 72 hours |
8. What it costs
| Item | USD | CNY |
|---|---|---|
| PKD1 swab | 40 to 80 | 100 to 250 |
| F9 clotting DNA test | 60 to 120 | 150 to 350 |
| Kidney ultrasound | 120 to 250 | 300 to 700 |
| Echocardiogram | 220 to 450 | 600 to 1,200 |
| APTT plus factor IX assay | 80 to 200 | 200 to 500 |
| Year one total | 450 to 900 | 1,100 to 2,600 |
9. Five steps this month
- Ask the breeder for PKD1 and F9 certificates before the deposit.
- Book the 10 to 12 month kidney scan and the baseline echo for the same morning.
- Start the water and litter log tonight; 45 mL/kg is the line to beat.
- Tell every vet who touches this cat that a clotting panel exists, before any extraction.
- Diarise the 24 month kidney scan now, because the second look is the one that clears the cat.
PKD is confirmed on ultrasound, HCM on echo, hemophilia B on a factor assay, ALPS on a blood count and biopsy. The value of the 2 swabs is that they arrive before the first anaesthetic rather than after it. Weight is the cheap half: a 5% loss in 30 days or a 10% gain in 90 days is the same trigger used in the British Shorthair weight guide.
Terms mentioned in this article
Frequently asked
Can I skip the kidney scan if the PKD1 swab is negative?
Not in this breed. The swab is useful and cheap, but its validation is less settled here than in the Persian family, and cysts are what actually change management. Scan at 10 to 12 months and again at 24 months, then stop if both are clear.
Why does hemophilia B matter before a dental?
Because a prolonged APTT with a normal platelet count is the pattern that turns a routine scaling into a bleed. Ask for the clotting panel before any extraction, tell the vet a result exists, and keep vaccines subcutaneous rather than intramuscular.
What does the first year of screening cost?
About 450 to 900 dollars, or 1,100 to 2,600 CNY, for the PKD1 swab, the F9 test, a kidney ultrasound, a baseline echo and an APTT with factor IX. The two DNA tests are one-time costs and do not repeat.